Complex sentence: Campaign mode has just one axis campaign called The Kanal Front for attacking English targets in the channel and in southern England after 1943.The allied campaign called Fortress Europe is to attack the axis in the European Theater of Operations in 1944 before and after D-Day.
Split into simpler sentences: Campaign mode has just one Axis campaign, The Kanal Front, in which you attack English targets in the Channel and in southern England after 1943. The objective of the campaign is to attack Axis positions in the European Theater of Operations during 1944 before and after D-Day.