On 26 May 1940 Tennant was appointed Senior Naval Officer ashore at Dunkirk, and ordered to Dover, where he took command of a naval party of eight officers and 160 men. Tennant's party was dispatched on board the destroyer to aid in the evacuation of more than 300,000 British and French troops left stranded when France fell to the Nazis. Tennant's task was to organize the men and get them onto the ships waiting to take them. Tennant stayed right up until the last ships left on 2 June, patrolling the beaches of Dunkirk with a megaphone searching for British troops.