Suursaari is a long, narrow shard of granite — about eleven kilometers from end to end — sitting almost exactly in the middle of the Gulf of Finland. To Finland, it was a sentinel guarding the southern approaches. To the Soviet Union, it was a threshold to Leningrad, the second city of the empire. In March 1939, Stalin asked Finland to lease it for thirty years along with several smaller islets, and to cede populated territory on the Karelian Isthmus that he said was vital to defending Leningrad against a possible German attack. The Finns, who knew exactly what 'leasing' to a great power tended to mean, refused. The Winter War followed within months. Under the Moscow Peace Treaty that ended it, Suursaari passed to the Soviet Union — until the next war scrambled the map again.

When German forces drove on Leningrad in late 1941, the Soviet command pulled back from many of the Gulf of Finland islands to consolidate around the besieged city. Soviet garrisons left Gogland, Sommers, and Bolshoy Tyuters between 7 and 9 December 1941. Finnish coastal troops noticed within days and slipped small detachments onto Gogland and Sommers. Then weather and ice intervened. A blizzard cut off the new garrisons; a Soviet company-strength force returned on 2 January 1942 and forced the surprised Finns off Gogland. By spring the situation had locked into a stand-off — five hundred Soviet defenders dug into the rocks of Suursaari, no artillery to support them, the ice thick enough to drive guns across. The Finns planned accordingly.

The assault force was built around two task groups: the larger Detachment Sotisaari approaching from the west, the smaller Detachment Miettinen pinning down the east side of the island. Two ice roads were prepared. Trucks rolled into position before dawn on 27 March, then handed off to skiers for the final five kilometers. Air activity above the Gulf was furious. Finnish Fokker D.XXI, Curtiss P-36 Hawk, and Brewster F2A Buffalo fighters tangled with Soviet Polikarpov I-153 biplanes and I-16 monoplanes, claiming twenty-seven Soviet aircraft over two days. Finnish Bristol Blenheims and captured Tupolev SB-2 bombers worked over the Soviet positions. The defenders, without artillery and without air cover, fought until small parties broke off and fled across the ice toward Moshchny Island. Finnish fighters strafed them as they ran.

With Suursaari taken on 28 March, the Finns turned to neighboring Bolshoy Tyuters. A first patrol on 30 March was driven off by a strong Soviet garrison. A larger company-sized force on 1 April found the island suddenly empty — and the next day watched Soviet troops return and dig in. With German support the Finns eventually cleared the island. On 8 April, after the Germans had hauled artillery onto Bolshoy Tyuters, a Soviet counter-attack of roughly twelve hundred men crossed the bare ice to retake it. Without cover and against properly emplaced guns, they suffered terribly. The attack failed. The Finns then handed Bolshoy Tyuters over to the Germans, who held it until they evacuated Estonia in 1944. The wider goal — taking every major island in the eastern Gulf — failed because the German troops needed for it were pulled back to defend the Leningrad Front.

Suursaari/Gogland remained Soviet after the war and is today part of Russia's Leningrad Oblast, an off-limits military zone that even Russian citizens need permits to visit. The wrecks of warships sunk in the surrounding waters still litter the seabed; the rocky shoreline is dotted with rusting bunkers and gun emplacements from both wars. From cruising altitude over the Gulf of Finland, the island appears as a long dark sliver pointing roughly north-south, alone in pale water that freezes solid in winter and turns brilliant blue in summer. Pilots flying the busy corridor between Helsinki and Saint Petersburg pass within sight of it on most clear days, usually without realizing they are looking down at one of the only places where soldiers fought a battle on a frozen sea.