During the Summer War in 1941, the Finns were content to disturb the supply of and contain the Soviet garrison at Hanko. Here, light mortars are shown firing from their protective trenches on the Hanko front. At the start of the war, the Soviet naval base on the leased Hanko Peninsula had been surrounded by Group Hanko. This included the 17th Division and the 4th Coastal Brigade. The Finnish Navy tried to disrupt the Soviets from reinforcing their garrison and applied pressure from the cover of the nearby archipelago. At its height, the Soviet troops at Hanko numbered around 35,000 men, supported by heavy artillery and tanks. The main fear at the time was that this strong force would attack straight into western Finland. In general, the Finns were content to leave the Soviets alone and tried to soften the motti rather than risk losing men in capturing the base. With winter drawing near, the position of the Red Army and Navy at Hanko became more precarious. During the thaw and the season of open seas, the relatively weak Finnish Navy was unable to bring about a decisive victory. However, the ocean would soon freeze, allowing the army to bring in overwhelming numbers. Therefore, on 2 December 1941, the Soviets abandoned the area under the cover of darkness.
Book "Finland at War: The Continuation and Lapland Wars 1941-45" by Vesa Nenye, Peter Munter, Toni Wirtanen and Chris Birks