The hunt for the German ’pocket battleship', which had been attacking merchant ships in the Atlantic early in World War II, leads a squadron of British cruisers into a fierce battle, before the Graf Spee takes refuge in the neutral port of Montevideo. The script was partly based on Captain Dove's account of being captured by the Graf Spee, whose captain is portrayed with quiet dignity, leading up to his decision to scuttle the ship.
The Battle of the River Plate was apparently prompted by an invitation to the Mar del Plata Festival in 1955. Pressburger suggested that the hunt for the German ’pocket battleship' Graf Spee, driven into Montevideo by the courageous action of a British cruiser group in the early months of the war, might be a promising subject. The logistical requirements for such a film were formidable. Four warships were needed to manoeuvre at sea to reproduce the attack. What interested Powell and Pressburger as much as the David and Goliath battle itself was the response of two sets of onlookers: the British merchant seamen rescued by the Graf Spee from its earlier raids and held captive on board throughout the engagement; and the intensive diplomatic activity that converged on Montevideo during the tense hourse while the Graf Spee's captain pondered his final move.
Ian Christie (Michael Powell & Emeric Pressburger: Arrows of Desire)