What was the lonest lasting military engagement of World War 2?

The longest lasting military engagement of World War II was the Battle of the Atlantic, which lasted from September 1939 until the defeat of Nazi Germany in May 1945. This protracted conflict involved naval warfare between the Allies and the Axis powers, primarily focusing on the struggle for control of the Atlantic sea routes. It included extensive submarine warfare, convoy battles, and air attacks, significantly impacting the supply lines vital to the Allied war effort. The battle was crucial for maintaining the flow of troops and materials necessary for the Allies to sustain their campaigns in Europe.