Bismarck would make the Saint-Nazaire raid urgent and harder

Would the Royal Navy rush the Saint-Nazaire raid if Bismarck reached the dry dock?

Probably, but denser defenses would make success much less likely unless a bombing diversion distracted the harbor at the critical moment.

The Royal Navy would probably accelerate the Saint-Nazaire raid because the dry dock now contained the very battleship Britain wanted to deny Germany. Campbeltown's historical approach depended on deception and surprise rather than winning a conventional fight through the harbor defenses. Bismarck would attract more patrol boats, minesweepers, aircraft, and troops, increasing the chance that the raiders were detected and stopped before reaching the caisson. The ship herself could not usefully fight from blocks in the dock, but the surrounding security response would be formidable. Synchronizing a bombing raid with Campbeltown's arrival could force defenders to look upward while the destroyer made its run.