Admiral Graf Spee had fought a series of relatively easy actions against ships that did not fire back. At the River Plate, the opposing warships returned fire and forced it into a harder fight. German expectations of victory rested on facing a light cruiser and two destroyers. The British force actually comprised a heavy cruiser and two light cruisers, so that assessment understated the opposition.
Notable Point · 3:14-3:42
Graf Spee underestimates the British cruiser force
A mistaken assessment of the British ships helps explain Graf Spee's expectation of victory after earlier actions against merchant shipping.