Which battalion did Winston Churchill command during World War I?

During World War I, Winston Churchill commanded the 6th Battalion, Royal Scots Fusiliers.

After resigning as First Lord of the Admiralty in November 1915, Churchill returned to active military service on the Western Front. He was attached first to the 2nd Battalion, Grenadier Guards, and in January 1916 was temporarily promoted to lieutenant-colonel and given command of the 6th Battalion, Royal Scots Fusiliers.

The battalion served near Ploegsteert on the Belgian section of the Western Front. Churchill spent roughly three months with it under continual shellfire, visiting trenches and directing its activities. In May 1916, the 6th Royal Scots Fusiliers were absorbed into the 15th Division, and Churchill left active service rather than seek another command.

This episode is often overlooked because Churchill is chiefly remembered as a politician and wartime prime minister. It also explains why answers naming a Guards battalion can sound plausible: he served with the Grenadier Guards immediately before commanding the Royal Scots Fusiliers, but he did not command the alternative units listed here.