The bluff is a tactic often used to deceive an opponent into believing that your hand is stronger than it really is. For example, when playing poker, you might bet heavily with a weak hand in an attempt to convince other players to fold.
In 1939 at the outbreak of WW2, Hitler ordered the German Navy, to intercept and destroy Allied merchant ships. Between September and December 1939, the German heavy cruiser, Admiral Graf Spee, was highly effective, sinking nine merchant ships in the South Atlantic. The Admiral Graf Spee was a formidable armoured ship with six 28cm guns and a top speed of 28 knots which meant that very few ships of the British or French navies could catch her. She was commanded by Captain Hans Langsdorff who was born in 1894 and who had been awarded the Iron Cross for his actions as a lieutenant in the German navy in WW1.
The British sent three light cruisers to intercept the Admiral Graf Spee and they engaged her in the Battle of the River Plate on 13 December 1939. The German ship inflicted heavy damage on the British ships but she too was damaged and retreated under a smokescreen into the port of Montevideo in Uruguay.
While the Admiral Graf Spee was moored in Montevideo for repairs, British naval intelligence worked to convince the Germans that a vastly superior force was concentrating outside Uruguayan waters to destroy the ship, if it attempted to break out of the harbour. The Admiralty broadcast a series of signals, on frequencies known to be intercepted by German intelligence. Such reports were also leaked to the press in South America. In reality the closest heavy units—the carrier Ark Royal and battlecruiser Renown—were over 2,500 miles away, much too far to intervene. Believing the British reports, Langsdorff discussed his options with his commanders in Berlin. His choices were either to break out and seek refuge in Buenos Aires, where the Argentine government (which was sympathetic to Germany) would intern the ship, or to scuttle the ship in the Plate estuary.
Langsdorff was under instructions from Berlin not to let his ship fall into enemy hands and he was unwilling to risk the lives of his crew, so he decided to scuttle the ship. This took place on 18 December. The British had bluffed the Germans out of one of their most potent weapons.
Hans Langsdorff must later have realised that he could have outrun the British and reached Buenos Aires and safety. On December 20, in his hotel room he shot himself. He was in full dress uniform and lying on the ship’s battle ensign. The ship’s crew were taken to Argentina, where they were interned for the remainder of the war.