Answer:
Mediterranean Front
Retake North Africa
Attack Italy from the south.
In the Mediterranean, the allies first took control of North Africa from the Axis, and then, launched the invasion of Italy from South to North.
Eastern Front
Support the USSR
Attack Germany in the east.
In the Eastern Front, the USSR practically fought Nazi Germany alone. This front was the deadliest of the war. The other allies gave technological and economic support to the USSR, but did not really get involved in the battles.
Western Front
Invade France from Britain
Attack Germany in the west
The strategy of the Western Front consisted first in the invasion of France (controlled by Nazi Germany at the time) from England. This was accomplished with the Normandy Landings.
Then, from France, and later from Belgium and the Netherlands, the allies invaded Germany in the west.