It has been described Statement as the first major military campaign Military_operation fought Hostile_encounter entirely by air forces .

The Germans had attacked Attack a weakly defended Defending section of the Allied line , taking Conquering advantage of heavily overcast weather conditions that grounded Placing the Allies ' overwhelmingly superior air forces .

The initial plan Arranging was to push Denmark to accept Agree_or_refuse_to_act that German land , naval and air forces could use Using Danish bases , but Adolf Hitler subsequently demanded Request that both Norway and Denmark be invaded Attack .

This was the first large-scale operation Military_operation by the Allies of World War Military_operation II combining Cause_to_amalgamate sea , land and air forces .

Convoys , coming Self_motion mainly from North America and predominantly going to Self_motion the United Kingdom and the Soviet Union , were protected Preventing_or_letting for the most part by the British and Canadian navies and air forces .