What military strategies contributed to the allied victory in world war II?

Military
intelligence played a key role in the Allied victory of WWII.  By 1943 the Allies had broken the
key military and diplomatic codes for Germany and Japan and often had a better idea about the
battle plans than the Axis generals.  Strategic bombing also played a key role by hitting
industries such as oil, electricity, and manufacturing that made mechanized war possible.  The
Allied use of the Norden bomb sight made strategic bombing easier, as bombers could now adjust
for the speed of the plane and wind speed when dropping bombs.  While the Germans did this as
well with their Luftwaffe, the Allied use of air support in ground campaigns, especially after
D-Day was essential.  By late 1944 the Allies nearly had complete air superiority over the
Germans in this war of attrition.  In naval warfare, Allied forces brought back the convoy
system which kept destroyers and cruisers close enough to attack German U-boats.  The U-boats
would continue to be a threat, however, until the concrete submarine pens were captured in
France after D-Day.  

In the Pacific Theater, Douglas MacArthur used an
island-hopping campaign that captured key islands which were then converted to American air
bases.  This ultimately allowed American bombers to firebomb the main Japanese island of Honshu
with as little loss of American lives as possible.  American submarines preyed relentlessly on
the Japanese merchant marine, and by summer 1945 Japanese civilians faced shortages and
starvation.  Of course, probably the greatest strategy was the use of two atomic bombs in quick
succession to bring about the end of the war.