Initially the Vyborg Bay islands were in a fairly strong position with the Finnish garrison on the Koivisto islands preventing Soviet naval forces from gaining access to the bay. The Soviet Baltic Fleet landed a small assault force on the islands, but the Finnish garrison managed to keep the bridgehead contained. Nevertheless, Finnish headquarters decided it would be impossible to keep the troops in the islands supplied given Soviet air supremacy, and withdrew their forces from the islands unopposed. This opened the route for the Baltic Fleet to get safely into the bay.