In the history of Russia as a European and world power, its Navy has always taken an important and appreciable place. In the present day complicated situation in Russia, the 300th anniversary of our Navy bids us once again to reconsider its history and present condition in order to determine the optimum trends of its development, training and application in the first half of the 21st century without repeating past mistakes.
The geopolitical, geostrategic and geoeconomic situation of Russia, with its coasts washed by 12 seas, with more than 70 percent of our state frontiers passing through sea waters and with a coastline of about 100,000 kilometers, with the most important and the most prospective part of national economics being the rich natural resources of the seas and continental shelf, definitely put our country into the number of the world’s greatest sea powers.
The first to understand this was the famous reformer of Russia, Peter the Great, who, 300 years ago, on the 20th of October 1696, founded the Russian fleet. Only after victories over its strategic enemies on the Black and the Baltic Seas, gained under the personal participation of Peter the Great, was Russia recognized in Europe as a great power (empire), and Peter the Great was considered to be an emperor. With his genius and his efforts a powerful state was created, a strong fleet founded, and glorious traditions laid, on the basis of which Russia’s fleet has gained the greatest number of victories among all other fleets of the world. Our Navy still sticks to these traditions and its mottos are: Motherland, Fortitude, Honor.
The first Russian submarine project was submitted to Peter the Great in 1718 by the peasant Efim Niconov, and in 1723-1732 it was constructed. This trend in the construction of Russia’s Navy got its further development only in the first half of the 19th century, after the successful experiences of the American engineers Bushnell and Fulton, when the Russian military engineer Karl Shilder became engaged with it.
But the first submarine with a mechanical engine in Russia was
constructed and tested in 1863-1866 in the Baltic plant by engineer Ivan Alexandrovskiy. By 1874 he had created and tested a selfpropelled torpedo for his submarine. S. Dzhevetskiy was the first in Russia to design, construct and test a submarine with an electrical engine in 1876-1879. And, in 1879-1881, 50 submarines were constructed under his last project.
In 1900-1903 under I. Bubnov’s and M. Beklemeshev’s project the first combat submarine DOLPHIN, with above-water and underwater movement engines, was constructed. This submarine was armed with two torpedoes and a machine gun and could travel 60 miles at a speed of 5 knots in a submerged condition, and 1000 miles at a speed of 7 knots in the surfaced condition. In 1904 DOLPHIN was in the Baltic fleet, and then was carried by railway to the Far East. During the war with Japan, six various types of submarines were constructed in Russia. Part of the submarine fleet was engaged in combat operations.
On the 19th of March 1906 a decree was signed by Emperor Nikolay the Second for the creation of submarine forces for Russia as a part of the Baltic fleet, with the first formation of submarines situated in Libava. In all, during the period of 1900-1917, 95 submarines were laid down and constructed in Russia.
In the course of the First World War of 1914-1918, Russian submarines were widely engaged in combat operations against Germany’s Navy on the Baltic Sea. After the end of the Civil War Soviet Russia had only 9 submarines fit for further employment. Having drawn the right conclusions from the results of sea fights of the First World War, in which about 6000 ships were sunk by submarines (while only 217 ships were sunk by surface ships), Soviet naval science of the 1920s and 1930s considered the submarine force to be one of the main arms of the Soviet Navy. Within the period of 20 years before the beginning of the Second World War, the Russian Navy, which had been destroyed during the Civil War, was reconstituted on the new technological basis. By the Spring of 1941 it was formed of 1000 combatant ships and vessels, including 3 battleships, 7 cruisers, 59 destroyers, and so on. The quantity of submarines in the Russian navy exceeded the quantity of submarines in the navies of any country of that time. The Soviet Union had 218 submarines, Germany-165, Italy-93, Japan-63, USA and Great Britain together had 168 submarines. And Soviet submarines of classes S and K were quite up-to-date, submarines of class K were considered to be the fastest and to have the strongest armament in the world. The realization of the leading role of submarine forces in other navies occurred in the course of the war: Germany constructed 1131 submarines, the US Navy and the Royal Navy had 463 submarines.
Submarine forces of the Soviet Navy by June of 1941 had the following disposition: the Northern Sea Fleet-15 submarines; the Baltic Fleet-68; the Black Sea Fleet-44; the Pacific Fleet-91; with the objective of braking the enemy’s sea communications. In evaluating the war potential of the Soviet Navy of that time it is necessary to note the negative influence of the lack of connection between the fleets and theaters of war, the very low possibility for maneuvers between theaters of war and the capability of the Navy to conduct combat operations only in inland waters because of the lack of aircraft carriers, and an insufficient number of ocean submarines and big ships.
It was possible for the German Navy to increase its power on the Baltic Sea, as well as on the Northern Sea and on the Black Sea, because Germany had in its hands straits and coasts along which it used to carry out strategic shipping, especially on the Baltic and the Barents Seas. The German Navy gained a lot of advantages from this situation in the initial stages of the war.
The Soviet Navy was the only armed service which was not taken unawares by the sudden enemy aggression on the 22nd of June 1941. By order of the Navy Commander-in-Chief Admiral N. Kuznetsov, all fleets were given the alarm in proper time and could in, an organized way, repel the first attacks of the enemy. In the first half of the 22nd of June, 15 submarines of the Baltic, Northern and Black Seas occupied combat positions.
In the course of the war from the very beginning up to the end on the 2nd of September 1945, Soviet sailors, as well as submariners, never retreated. In all of their combat they showed a high level of battle training, fortitude, courage and bravery, according to the best historic traditions of the Russian Navy.
Submarines of the Northern Sea Fleet laid mines at the entrances to the enemy’s ports, destroyed enemy transport and combatant ships in and near ports using torpedoes and artillery fire, and operated independently on the seas protecting allied convoys in our zones.
But in spite of replenishment of the fleet by new submarines it still did not have enough forces. According to the Navy Commander-in-Chiefs decision in 1943 five submarines from the Pacific
Fleet arrived in the Northern Sea Fleet, having traveled 17 ,000 miles through the Pacific and Atlantic Oceans.
To raise the effectiveness of combat operations in 1944 submariners, instead of acting in the sea positions, began to use submarines to make up beetled (over Norway coast) screens in cooperation with torpedo boats and the fleet’s attack aviation using air reconnaissance data. During the war submarines of the Northern Sea Fleet made over 300 combat patrols and destroyed about 250 enemy transport and combatant ships. In these operations the fleet lost 22 submarines.
On the Black Sea combat operations of the Soviet submarines were directed against enemy sea shipping near the Romanian coast, and to blockade the Bosporus. After the occupation of the Crimea and the blockading of Sevastopol, the Black Sea Fleet’s submarines were transferred to the Caucasus ports. From there they delivered ammunitions, nourishment and fuel to the beleaguered Sevastopol, taking wounded away from the city.
In 1943-1944 the activity of the Black Sea Fleet’s submarine forces was directed toward breaking near and remote communications of the enemy, and to prevent the enemy’s evacuation. Fulfilling these missions, our forces annihilated more than 42,000 fascists near the Caucasus coast. During the years of the war, submarines of the Black Sea Fleet made over 200 combat patrols and destroyed over 100 enemy transport and combatant ships. In these operations the fleet lost 27 submarines.
The Baltic Sea Fleet’s submarines conducted their combat operations in most unfavorable conditions. By the end of August 1941 the fleet had lost almost all its naval bases including the main base in Tallinn. The submarines forces had to be based only in Leningrad and Kronstadt, having the very straitened and shallow eastern part of the Gulf of Finland for deployment.
Submarines of the Baltic Sea Fleet acted against enemy communications near Swedish coasts and laid mines near enemy naval bases. The resistance of the enemy in the Baltic Sea was very powerful. Antisubmarine warfare in the Gulf of Finland consisted of 66,542 mines of various types, a lot of antisubmarine nets were set and about 150 fascist ships and vessels conducted combat operations. In these conditions, submarines of the Baltic Fleet in 1941-1942, made more than 110 combat patrols, destroyed about 80 enemy transport and combatant ships, having complicated considerably German strategic sea shipping on the Baltic Sea. But, during the first 18 months of the war, the Baltic Fleet lost 40 submarines because of mines and antisubmarine obstructions, and the Navy Commander-in-Chief N. Kuznetsov temporarily prohibited them from going out to sea.
The Baltic Sea submarines resumed combat operations in September 1944 from the ports of defeated Finland. During the eight months before the end of the war they destroyed 72 enemy transport and combatant ships. The most glorious victories were gained by the submarine LEMBIT under command of Captain of the Second Rank A. Matiyasevich-25 victories included 22 transport and combatant ships destroyed by him personally, and the submarine S-13 under command of Captain of the Third Rank A. Marinesko, who in January 1945 in one cruise, destroyed the fascist military transport ship WIT.LIAM GUSTLOV of 25,484 tons and then the transport ship GENERAL VON STEUBEN of 14,660 tons. These ships carried 10,000 fascists including 3000 submariners. This allowed S-13 to take first place in the Soviet Navy in the total displacement of destroyed enemy ships.
The results of the war confirmed the correctness of the Soviet military scientists’ prognosis: submarine forces as well as aviation had become the main armed services of the Navy. Aviation destroyed 55 percent of all ships sunk of Germany and its allies in the East Front, and submarines sank about 33 percent of all annihilated ships.
In our seas the enemy lost 48 submarines; our Navy-95, with most being lost in the initial period of the war, 1941-1942, which was most unfavorable for our country. Total losses of the German submarine fleet in this war were 768 submarines, that is 64.5 percent of their total quantity. Our losses amounted to 35 .2 percent (including 54 submarines constructed during the war). And these figures show higher combat skills of the captains and crews of our submarines.
These experiences of the war showed the necessity of providing global combat support of submarines by other armed services of the Navy, first of all by surface ships and aviation. In the whole, the Soviet Navy and its submarine forces honorably fulfilled their tasks in the Great Patriotic War and proved their capability to defend the sea frontiers of our country.
Global geopolitical differences between the USA and USSR, creation of NATO in 1949 and, in response to it, creation of WTO (the Warsaw Treaty Organization) in 1955 led to the Cold War and escalation of the armaments race. Taking into account our considerable lack of submarines (in 1945 the USA and GB had 463 submarines; the USSR-172 or 37 percent) the Soviet Union had constructed by the late ’50s 265 conventional-electrical submarines of the first after-war generation.
For the purpose of protecting its communications and defending 12 seas which surrounded the USSR, part of which were closed sea theatres of operations, the Soviet Union continued to construct conventional-electrical submarines. After 1958 more than 120 submarines of this type (project 641-Foxtrot class, project 641BTango class and project 877-Kilo class) were constructed for the Navy and for export.
But yet from the early ’50s, on the basis of the latest achievements of science and engineering, it became clear that the main and most prospective trend of development of the submarine forces was in the design and construction of nuclear powered submarines. In September 1952, a decision was taken to design the first nuclear powered submarine (called NOVEMBER) in the Soviet Union. In September 1955 it was laid down in Severodvinsk, and in 1958 it was delivered to the Navy. By 1964 12 more submarines were constructed and delivered to the Navy.
The introduction of nuclear technology in the construction of the Soviet Navy led to the appearance of three classes of nuclear powered submarines: strategic (SSBN), attack (SSGN) and multipurpose (SSN). The USSR was the only country to create three classes of combat nuclear powered submarines at a time. A characteristic feature of the period in which nuclear powered submarine fleets were formed was that the United States, after long research and construction of eight nuclear powered submarine projects, chose in the early ’60s two main projects, while the Soviet Union constructed 11 different projects of nuclear powered submarines up to the early ’80s. That large number of submarine classes greatly complicated the operations and performance of the force.
During 1961-1970 the USA constructed 78 nuclear powered submarines (including 41 SSBNs which carried up to 70 percent of the American strategic nuclear offensive potential) and the Soviet Union began to construct nuclear powered submarines of the second generation. By 1974 the biggest series was created in the history of nuclear powered submarine construction: an SSBN series of 34 nuclear powered submarines of project 667 A (Yankee class) which in its further modifications (Delta-1, Delta-2, Delta-3 and Delta-4) amounted to 77 submarines by 1990.
The period from the middle ’60s up to the early ’80s is considered to be the Golden Age of the Soviet military ship construction. The USSR Navy successfully developed the process to attain military parity with the US Navy. That became possible due to an increase in the quantity of the ships. All this contributed considerably to the maintenance of international stability.
In this period the US Navy constantly had about 24-25 (of 41) SSBN on combat patrolling in the open seas. It means that the efficiency of the operational employment was about 0.6. Besides that, up to 20-25 multipurpose submarines (SSN) constantly were in the open seas. In total they took 210-230 cruises per year. Lack of a systematic character in the Soviet Navy construction and the low developed infrastructure of the Navy resulted in an efficiency of the operational employment of our submarines of half that and we could maintain parity in the seas only by having two times as many submarines.
In the early ’80s we managed to overcome the technological lag and to considerably improve the characteristics of our submarines. The third stage in the history of Russia’s nuclear powered submarine fleet was marked by the appearance of a new type SSBN (Typhoon) in 1981. Six submarines of the class were constructed up to 1989. At the same time seven Delta-4 SSBNs, which had the same range of fire, were constructed.
Besides that, from 1980 up to the present time the SSGN Oscar class (with 24 SLCM Granit) is being constructed. At the same time, along with the third modification of the nuclear powered multipurpose submarine Victor-3, from the middle ’80s SSNs of the new projects Sierra and Akula, with quite similar characteristics, are being constructed. The experience of combat patrolling of submarines of this type during the last few years shows that former shortcomings of Soviet nuclear ship construction, such as high noisiness, are basically eliminated. In 1993 an SSN of a new generation, SEVERODVINSK, was laid down.
The composition of the Soviet submarine fleet met the requirements determined by Soviet military doctrine. Our Navy was in all important zones of the world and had operational and tactical contacts with ships and forces of the US Navy and NATO. Our ships and sailors were not inferior to American ships and sailors. In the early ’90s, the senselessness of political and military opposition between the USSR and the USA, WTO and NATO, became clear. That9s why START I and START II were signed in 1990 and 1993, and according to those treaties the quantity of SSBNs in the Russian Navy is to be reduced from 62 to 25, and the quantity of SSBNs in the American Navy is to be reduced from 36 to 14.
But global changes which had occurred in the world after the end of the Cold War, and had reduced considerably the threat of worldwide nuclear war, did not reduce the danger for the world community in whole, and for many states in particular. A new danger is represented by local and regional armed conflicts of different scale and intensity, which will be the most probable method of resolving ethnic, religious, economic, territorial and other disputes between states. This is confirmed by the developments in the Caucasus, on the south borders of the former Soviet Union, in the Middle and Far East, in Yugoslavia and so on. Most of these hot points are situated near Russia’s borders.
The policy conducted during the last decade by our leadership on the basis of new political thinking for our country and the whole world did not lead to the expected stabilization of the international situation. On the contrary, the situation became more complicated and tense. Unilateral self-dissolution of the WTO did not cause the dissolution of NATO. According to the specialists’ estimations the number of countries possessing nuclear armament and means of its delivery will increase to 20-25 in 2003. The struggle between world powers for economic and political influence worldwide and regionally, for possession of sources of raw materials and so on, shows that the transition to the 21st century will not be quiet and serene.
Analysis of the condition and prospects of development of the NATO navies, and those of other countries, for the next 20-25 years shows that all these countries continue to strengthen and improve naval components of their armed forces. Construction of up-to-date ships and submarines (including nuclear powered attack submarines in the USA, France, Great Britain and China; submarines armed with SLCM (Submarine Launched Ballistic Missile); and nuclear powered aircraft carriers in the USA and France) will increase considerably the combat potential of these countries in the beginning of the 21st century.
Analyzing the condition and destination of our Navy during the last 10 years, it is easy to understand that, being reduced by half, it was, and remains, destined to conduct defensive sea operations: about 60 percent of its ships are the ships of local seas and only about 15 percent are the ships of open seas.
If the disintegration processes on the territory of the former Soviet Union will not be stopped, if insufficient providing for the Navy of money, ship repair, men, fuel, materiel and so on, will be continued, we, according to some estimations, in 2000 will not have more than 7-10 SSBNs with limited periods of employment, 15-20 SSNs and 10-12 conventional submarines. On the Baltic Sea we will be two to three times weaker than Sweden and five times weaker than Germany; on the Black Sea we will be two times weaker than Turkey and if we lose Sevastopol, the main naval base of the Black Sea Fleet, five to seven times. In the Far East our Pacific Fleet has three times less ships than Japan (Japan and the Pacific Fleet have an equal number of torpedo submarines, but Japan has to protect its 1000 mile zone and we have the shortest distance from Vladivostok to the Chukotski Peninsula of 2500 miles). In total our combat potential is comparable with potentials of Great Britain or France. But it is necessary to take into account that our sea frontiers are 15-20 times longer and our economic sea zone and continental shelf are considerably wider, so it is easy to understand that we have less possibilities to protect both our frontiers and our national interests at sea.
If Russia has not the naval power able to restrain the hostile intentions of others and to decrease the appetites of its neighbors, in the complicated, multipolar and dynamic situation on the Baltic and Black Seas, it will be 200-300 years behind other countries in the geostrategical aspect. Then, similar events will occur in the Far East.
So, appraising geostrategical, geopolitical and economic conditions of Russia on the threshold of the third millennium, we can come to a conclusion that the Navy continues to be one of the most effective instruments of the state policy oriented to secure constant economic and foreign policy interests of Russia. In the view of its national security and significance, the role of this instrument will increase.
According to the adopted .. Principal Propositions of Russia’s Military Doctrine” the Navy, in the composition of armed forces, is tasked to secure sovereignty, territorial integrity and other vital interests of the Russian Federation. The priority mission or the Navy and other services of the armed forces, side by side with political, diplomatic, economic and other activities, is prevention of war and military conflicts, repulse of probable aggression, covering of the country’s objects, forces and troops from ocean and sea directions, infliction of defeat on enemy forces, creation of conditions for cessation of hostilities at the earliest possible stage and concluding of peace on conditions meeting Russia’s interests. Besides that, the Russian Navy can conduct peacekeeping operations under the direction of the UN Security Council or according to the international obligations of the Russian Federation.
Modelling opposing combat systems at sea is necessary to take into consideration the navies of neighbor countries. This is done by proceeding from the constant national interests of these countries, declared by them, (which do not coincide with our interests and which even contradict them), from the policy of the blocs they participate in, from the condition and perspectives of development of the navies as well as from real and planned employment of their navies in the time of peace and war.
With the purpose of fulfulling the armed forces’ and the Navy’s priority mission-prevention of war as part of forces of nuclear deterrence, maintaining strategical stability in a dynamic, multipolar and changing world, we must retain as a traditional component of our Navy-naval forces of a nuclear deterrent which have some advantages over strategic missile forces and strategic aviation.
With the aim of providing safe and secure functioning of these naval forces of a nuclear deterrent, in any conditions, as well as with the creation and maintenance of such an operational regime which will prevent the enemy from unleashing military conflicts, the Russian Navy must have in its structure general purpose forces.
The basis of the general purpose forces are submarine forces, which are the principal component of the Navy’s attack potential and are the most universal, mobile and powerful armed service able to fight with any kind of sea enemy. Surface ships, naval reconnaissance aviation, naval missile aviation, and naval antisubmarine aviation under the conditions of defensive doctrine, must become the main means of gaining supremacy in the near seas and of repelling an enemy’s aggression, in cooperation with submarines and other armed services.
Analysis of the experience of combat operations in the Persian Gulf shows that massed fire destruction of the terrain targets from
sea is realized by means of highly precise missile (SLCM) and air assault from submarines, surface ships, including deck aviation of the attack aircraft carriers, and by air attack forces form a distance up to 2500 kilometers.
Nuclear powered submarines are the very forces most efficiently capable of counteracting enemy naval forces carrying SLCM before they reach the open-fire line. They can create and maintain unfavorable conditions for the enemy, prevent missile assault against Russia and defeat the enemy after the beginning of the combat operations.
To provide secure combat activity of our naval forces of a nuclear deterrent, and fulfill missions of our general purpose forces, our Navy must have not less than 70 SSNs (50 of them being ready for action). Only half of our submarines meet this requirement. To retain this modem arm of the Navy it is necessary to construct a big series-about 30-40 SSN of a new type. Also our military science and industry must raise effectiveness, combat steadiness and vitality of submarines and surface ships by means of theoretical, constructive, technological and information support. Taking into consideration the physical and geographical peculiarities of our sea theatres of war and the geographical situation of Russia, it is expedient to have in the composition of our general purpose forces up to 30 up-to-date conventional-electrical, relatively inexpensive submarines (with 20-25 of them being ready for action) which will be sufficiently able to fulfill the same missions in the near sea zone on the Baltic, Black and Japan Seas.
Diminution of the quantity of submarines (less than 70 SSNs and 30 SSs) would prejudice, checked by combat experience, the strategic and operational conceptions of successfully conducting modem war at sea under the terms of Russia’s military defensive doctrine.
Analyzing surface forces, it is necessary to consider aircraft carriers of the Navy. The main destination of aircraft carriers of our Navy is to ensure combat steadiness. First of all in antisubmarine warfare and antiaircraft defense of operational forces of the Northern Sea Fleet and the Pacific Fleet while these forces fulfill the above mentioned missions of the general purpose forces.
Without such assistance at the lines from where the enemy will open fire against Russia, such powerful, multipurpose and mobile part of our Navy as submarines forces will suffer unwarranted and inadmissible losses before the beginning of combat operations and in the initial stage of it, that it will not be able to fulfill its missions in a proper way. The presence of the aircraft carriers in the composition of the operational forces of the Navy increases the effectiveness of submarine actions 150-200 percent, and decreases considerably the risk of losses.
So, by 2010-2015 it will be necessary to have the Navy composed of about 300 up-to-date ready for action ships (up to 85 submarines, up to 95 warships and up to 120 combatant vessels and near sea ships). It will be one third the quantity of 1990 but will improve 2.5 to 3 times the total combat potential for conducting defensive operations at sea. This quantity will allow the Russian Navy to keep parity with the forces of the US Navy, NATO, and other countries and blocs of the 21st century in the principal sea zones and regions in order to securely fulfill the missions of Prevention of Military Conflicts and Safeguarding of Peace and Stability at Sea.
Present temporary difficulties, mostly of an economic character, overshadow the acuteness of the situation and prospects of solving the problem of safeguarding Russia’s interests at sea, but if we do not see it in proper perspective and do not find the way to resolve this problem, in 1-2 years we will lose the most technological part of our shipbuilding industry, in 5-6 years we will lose the Navy. And it will take us not 10-15 but 30-40 years to revive it, with all the ensuring irreversible negative geostrategical, geopolitical and economic consequences.
To give a clear idea about the condition and prospects for solution of the strategic task of revival of Russia’s Navy, the author considered only one, the most tangible and visible, part of it-the ships and submarines. It is necessary to adopt a State program of revival of the Navy with stages of 10-15 years and 20-25 years. We think that, concerning ships, the program should include three levels: what, when and bow it is necessary to save from the present composition of the Navy with the aim to form a combat main body of the Russia’s future Navy; construction of new ships to substitute obsolete ones, ensuring the secure fulfillment of the missions of protection of Russia’s vital interests at sea; as well as participation in peacekeeping operations of the UN in the interests of world community in the main regions of the world for 20-25 years.
A country which is weak in world policy and economy can safely be ignored and its opinion usually is not taken into consideration. Russia must have a powerful Navy to save its traditional place of a great sea power to have prospects for its development in the 21st century as a strong, prospective and democratic state.
Admiral Gorbunov Alexandr Vasilievich was born on October 4, 1940 in Dzerzinsky and attended the Pacific Naval College and the Naval Academy.
Admiral Gorbunov began his service in the Pacific Fleet as a submarine torpedo group commander and continued as the commander of a submarine mine department and then as the 1st mate.
In the Northern Fleet from 1973 until 1987 he acted as 1st mate of a nuclear submarine, nuclear submarine Commander, Deputy Commander of the ships operational division and nuclear submarine Division Commander.
In the Black Sea Fleet from 1987 until 1990, he was the 1st Deputy Commander of the Flotilla and Commander of the operational squadron.
On the Main Naval Staff from 1990 until 1992, Admiral Gorbunov was the lst Deputy Commander of the Combat Training Department and from 1992 to the present he has been the Deputy Commander-in-Chief of the Navy for Combat Training and Chief of the Navy Combat Training Department.
1996 DOLPHIN CALENDAR
Welcome the new year with a 1997 Dolphin Calendar. Each time you purchase a calendar it helps to raise funds for the sons and daughters of our fellow submariners. This year the Dolphin Scholarship Foundation will provide 100 scholarships to very deserving and qualified students.
Large ($5. 75 each includes postage)
Small ($2.55 each includes postage)
Please send your name, complete address and phone number along with a check made payable to:
Dolphin Calendar Fund
1683 Dillingham Boulevard
Norfolk Naval Station
Norfolk, VA 23511