Holland was particularly involved in the attack on the French fleet at Mers-el-Kébir in July 1940. A British fleet, Force H, was despatched under Admiral Sir James Somerville to insist the French either demilitarize their ships or hand them over to the British, to prevent their capture by the Germans. Holland, as a French speaker with experience from his time as naval attaché in Paris, was sent to deliver the terms and enter negotiations with the French naval officers. He was taken into Mers-el-Kébir with the ultimatum aboard early on 2 July. Holland and Somerville were strongly opposed to the use of force, hoping that a show of strength would be enough to convince the French to avoid fighting.