The first USS Thatcher (DD–162) was a in the United States Navy, later transferred to the Royal Canadian Navy as HMCS Niagara. Construction and career United States Navy Named for Admiral Henry K. Thatcher, she was laid down on 8 June 1918 at Quincy, Massachusetts, by the Fore River Plant of the Bethlehem Shipbuilding Corporation. The ship was launched on 31 August 1918; sponsored by Miss Doris Bentley, the grandniece of Rear Admiral Thatcher. Thatcher was commissioned on 14 January 1919, Lieutenant Commander Henry M. Kieffer in temporary command. On 25 January, Lieutenant Commander Francis W. Rockwell—who later commanded the 16th Naval District in the Philippines at the outbreak of World War II in the Pacific—assumed command. Following shakedown, Thatcher operated with the Atlantic Fleet into the autumn of 1919. During the transatlantic NC-boat flights in May 1919, the destroyer operated on picket station number 9—one of 21 stations strung out from Newfoundland to the Azores—between her sister ships and . Underway at sea, she provided visual and radio bearings for the flying boats as they passed overhead on their way toward Lisbon, Portugal. Upon completion of this duty, the destroyer—reclassified as DD-162 on 17 July 1920—resumed her routine training operations off the eastern seaboard before heading west in the autumn of 1921 to join the Pacific Fleet. She operated out of San Diego, conducting exercises and training cruises off the west coast until decommissioned at San Diego on 7 June 1922. Thatcher remained laid-up at San Diego through the summer of 1939. War broke out in Europe on 1 September 1939, when German troops invaded Poland. Thatcher was recommissioned at San Diego on 18 December 1939, Lt. Comdr. Henry E. Richter in command, and conducted shakedown and training evolutions off the west coast until transferred to the Atlantic the following spring. Transiting the Panama Canal on 1 April 1940, a month before the situation in Europe became critical when Germany began her blitzkrieg against France and the Low Countries, Thatcher subsequently conducted neutrality patrols and training cruises off the east coast and in the Gulf of Mexico through the summer of 1940. The European situation took a drastic turn with the fall of France in June 1940. British destroyer forces in the wake of the Norwegian campaign and the evacuation of Dunkirk found themselves thinly spread—especially after Italy entered the war on Germany's side. Prime Minister Winston Churchill appealed