What was the most important battle of the war and why did the British lose the battle? PLEASE HELP

The Battle of Britain was a military campaign of the Second World War, in which the Royal Air Force and Fleet Air Arm of the Royal Navy defended the United Kingdom against large-scale attacks by Nazi Germany's air force, the Luftwaffe. It has been described as the first major military campaign fought entirely by air forces. The British officially recognize the battle's duration as being from 10 July until 31 October 1940, which overlaps the period of large-scale night attacks known as the Blitz, that lasted from 7 September 1940 to 11 May 1941.

Explanation:

lend lease program was passed by congress on march 11, 1941. the president could ship weapons, food, or stuff to any country whose struggle against the axis assisted u.s. defense

the northwest ordinance of 1787 guaranteed basic rights for settlers and banned slavery there.