Complex sentence: In the 1950s radar was being fitted to day fighters since the pilot could no longer see far enough ahead to prepare for any opposition, and since then the capabilities have grown enormously and are now the primary method of target acquisition.
Split into simpler sentences: In the 1950s, radar was fitted to day fighters, since pilots could no longer see far enough ahead to prepare for any opposition. Since then, radar capabilities have grown enormously and are now the primary method of target acquisition.