Complex sentence: The U-boat threat to supply convoys across the Atlantic made Saint-Nazaire a constant target of Allied air forces, in the face of determined Luftwaffe fighter opposition to the daylight raids by USAAF Eighth Air Force bombers.
Split into simpler sentences: The U-boat threat to supply convoys across the Atlantic made Saint-Nazaire a constant target of Allied air forces. In the face of determined Luftwaffe fighter opposition to the daylight raids by USAAF Eighth Air Force bombers.