May 31 in Military History

Samuel Pepys made his last diary entry, closing the most valuable first-person account of 17th-century English naval affairs, including the Anglo-Dutch Wars and the Great Fire of London.

President George Washington signed the Copyright Act of 1790, the first federal copyright legislation. The law established the legal framework that would govern U.S. military technical publication, service journals, and doctrinal manual publishing for more than two centuries.

The Treaty of Vereeniging was signed, ending the Second Boer War after nearly three years of conflict that had seen the British Empire deploy 450,000 troops against Boer guerrillas in South Africa.

The largest naval battle of World War I saw 250 ships and 100,000 sailors engaged in the North Sea, with heavy losses on both sides.

A magnitude 7.7 earthquake struck Quetta in British India at 03:02 local time. The disaster killed approximately 60,000 people including thousands of British Indian Army soldiers and dependents, destroyed the Quetta Cantonment, and reshaped British military construction standards across the subcontinent.

Three Japanese midget submarines penetrated Sydney Harbour in Australia, sinking the depot ship HMAS Kuttabul and killing 21 sailors in one of the most audacious submarine operations of the Pacific War.

Adolf Eichmann, the SS officer who organized the logistical infrastructure of the Holocaust, was executed by hanging in Israel after a landmark trial that brought the full horror of the Final Solution to global attention.

Crude oil reached the Valdez marine terminal via the Trans-Alaska Pipeline System, completing the 800-mile oil transport infrastructure from Prudhoe Bay. The project's strategic importance to U.S. energy security shaped Department of Defense contingency plans, Alaska Command operations, and Pacific Fleet tanker routing for decades.

Former FBI Associate Director W. Mark Felt revealed in a Vanity Fair article that he had been the anonymous source known as "Deep Throat" during Washington Post Watergate reporting. The disclosure closed a 33-year counter-intelligence mystery and reshaped FBI disclosure practices, whistleblower protection, and journalist-source protection policy.

The United States Space Command was reestablished as a unified combatant command, recognizing space as a warfighting domain and preceding the creation of the Space Force by six months.