3 submarine nets, coastal batteries and patrols by aircraft and light craft. Ice normally closes the Gulf of Finland from the end of December to early May, but the present winter is still mild and ice is of only sufficient strength to hamper movement at the extreme eastern end. Until the Red Army captures Tallinn and the Estonian airfields. the danger from the Soviet Baltic Fleet will be negligible. 11. The strength of the Finnish Navy is estimated at1 Armoured Vessel of 3,900 tons with four 10-inch guns.