A preposition is a word that tells you where or when something is in relation to something else. Examples of prepositions include words like 'after', 'before', 'on', 'under', 'inside' and 'outside'.
The Luftwaffe had already been a key part of the German advance through Europe. By the summer of 1940, Britain was their next target, though the RAF was a significant barrier. The main aeroplane ...