In the Continuation War the "ad hoc" Sissi Battalions were replaced by Independent Battalions. For example, the 4th Independent Battalion was directly under the command of Supreme Headquarters doing LRRP and raiding missions deep inside Soviet area. In the Battle of Ilomantsi, soldiers of the 4th disrupted the supply lines of the Soviet artillery, preventing effective fire support. In the Ladoga Karelia area of operations the length of the front, the absence of roads and a lack of troops prevented continuous front lines during the trench warfare period. Both armies used a chain of fortified field bases separated by the wilderness, monitoring and controlling the gaps with patrols. Both Finns and Soviets launched raids and recon patrols into enemy territory. Battles were short clashes of lightly armed infantry groups from squadron to battalion in size, with little chance of support or reinforcements.