Bastion ( naval ) A bastion in naval strategy is a heavily - defended area of water in which friendly naval forces can operate safely . Typically , that area will be partially enclosed by friendly shoreline , defended by naval mine s , monitored by sensors , and heavily patrolled by surface , submarine , and air forces . Soviet and Russian Naval Bastions . The bastion became an important strategy for the ballistic missile submarine fleets of the Soviet Union during the Cold War . The Barents Sea was made a bastion for the Soviet Red Banner Northern Fleet , and the Sea of Okhotsk for the Soviet Pacific Fleet , both of which remain important to the Russian Northern Fleet and the Russian Pacific Fleet . The Soviet Union had ( and , even more so , Russia now has ) limited access to the world ' s oceans : her northern coast is ice - bound at least the majority of the year , and access to the Atlantic requires transiting the GIUK gap ; much of her eastern coast is also ice - bound and requires moderately close approaches to either Alaska or Japan ; travel from her southern ports involves transiting first the Bosphorus and Dardanelles , and then either the Strait of Gibraltar or the Suez Canal . The Soviet Navy originally attempted to directly contest with the navies of NATO for control of the blue - water ocean . As the Cold War progressed , however , it became clear that the Soviets could not win a toe - to - toe fight in the deep water , and the information sold to the Soviets by the Walker spy ring in 1980s made it clear that the ballistic missile submarines , in particular , were very unlikely to be able to carry out their nuclear attack missions . Realizing their vulnerability , the Soviets adopted a two - level approach . They armed their older , noisier , and less reliable " second generation " ballistic missile submarines with shorter - range nuclear weapons and deployed them as close as possible to the United States . Soviet submarine K - 219 , which suffered a catastrophic explosion and fire off Bermuda on 3 October 1986 , was one such boat . Meanwhile , they used the information provided by Walker to build both dramatically improved attack boats such as the " Akula " - class , as well as more - survivable " boomers " such as the " Typhoon " - class armed with increasingly accurate and long - range missiles . Then they held those " third - generation " boats close to home , patrolling only near and under the Arctic ice cap . To secure the bastions , they also built large numbers of " Sovremennyy " - and " Udaloy " - class destroyer s , whose primary mission was anti - submarine barrier and picket patrol ; furthermore , the Soviet carrier - building projects were dedicated to defense of these bastions as well rather than independent strike groups , with Moskva - class limited to anti - submarine helicopters , Kiev - class carrying VTOL fighters as well as helicopters and a sizeable array of weapons ( hence the designation " aircraft - carrying cruiser " ) , and , finally , Kuznetsov class " heavy aircraft - carrying cruiser " fielding fixed - wing interceptors . The United States Navy practiced penetrating these bastions ; one such attempt resulted in the 20 March 1993 collision between USS " Grayling " ( SSN - 646 ) and K - 407 " Novomoskovsk " , a " Delfin " - class ballistic missile submarine . The collision was inadvertent and potentially catastrophic , but did demonstrate that US attack submarines were able to get rather near their intended prey . Chinese Naval Bastions . There are indications that the Chinese PLAN is adopting the concept as well , fortifying the Bohai Sea for use by its growing number of ballistic missile submarines . United States Naval Bastions . In the sense that a bastion is set up to protect the naval forces themselves rather than a land feature ( " e . g . " the Panama Canal ) , the United States Navy has never made significant use of the bastion concept .