Why did Captain Langsdorff choose to attack the British warships?
Langsdorff received intelligence that a convoy was preparing to leave the River Plate and that HMS Achilles was in Montevideo, presumably to escort it. In spite of problems with his main engines and other defects, Langsdorff decided that the sinking of a convoy and its warship escort offered a potential triumphant climax to a cruise that had so far yielded the sinking of only nine merchant ships. He considered he would be facing an inferior force and a sinking a convoy of merchant ships would most certainly further the main purpose of his mission.
Graf Spee sighted the British force at 0556 on 13th December, identified it initially as a cruiser and two destroyers and decided to attack. By the time Langsdorff realised he was up against three cruisers (far from an inferior force), it is questionable whether he could have disengaged without being spotted and shadowed. Had his Arado reconnaissance seaplane not have finally become unserviceable the previous day he would have known the strength of the British force earlier and probably would have been able to avoid action.