A considerable contingent from Lancaster accompanied Henry V in 1415 on a campaign that ended at Agincourt during the Hundred Years' War. John Lord Harcourt, bannert, took two knights, twenty-seven men-at-arms, and ninety archers; seven knights, James de Harrington, Richard de Kighley, Ralph de Stavely, Nicholas de Longford, William Botiller, John Southworth, and Richard de Radcliffe, and two esquires, John Stanley and Robert Laurence each served with fifty archers. In 1419 he was a commissioner to raise a loan for the King and in 1421 commissioner to bring 400 archers to France during the Hundred Years' War. He was knighted in 1417 or 1437 according to Schuyler Lawrence. Paul Lawrence believes it probably was 1417 as he is referred to as Sir Robert Lawrence in 1426.