Complex sentence: However, British intelligence had warned the French of the impending attack and the ensuing operation failed to achieve the strategic results desired by the "Oberkommando der Luftwaffe" (High Command of the Air Force).
Split into simpler sentences: However, British intelligence had warned the French of the impending attack. The operation failed to achieve the strategic results desired by the "Oberkommando der Luftwaffe" (High Command of the Air Force).