The Atlantic Theater refers to the military operations and battles that took place in the Atlantic Ocean and surrounding areas during World War II. This theater was crucial for controlling shipping routes and ensuring the movement of troops and supplies between Europe and North America. Key events included the Battle of the Atlantic, where Allied forces fought against German U-boats and surface ships. The Atlantic Theater also involved significant naval engagements, such as the Battle of Britain and the D-Day invasion. The efforts of the Allies, including nations like the United States, United Kingdom, and Canada, were vital in securing victory against the Axis powers in this region.