A founder member of the British Communist Party, Wintringham was the highest-ranking British Communist in the Battalion. He was the military correspondent for the Communist 'Daily Worker' and Editor of `Left Review'. He was university educated and fought in World War I rising to the rank of Captain. He was imprisoned in 1925 for inciting soldiers to mutiny.

From October 1936 Wintringham was a member of the Spanish Medical Aid Unit and a member of the militia `Tom Mann' Centuria after being given permission to give up his journalist role in Spain. He joined the British Battalion at Madrigueras and became machine gun instructor. While at Madrigueras he took part in the court martial, which led to the execution of the French officer DeLaSalle. Wintringham was appointed Commander of no 2 Company, the machine gun company. In February 1937 he replaced McCartney as Battalion Commander but was wounded within a few days at Jarama.

After Jarama he was made Commander of an NCO and Officer training school at Posarubio and later was made a Brigade Staff Officer. At Quinto in August 1937 he was wounded and returned home in November 1937.

It is possible that Wintringham was the first to think of the idea of the International Brigade. He left the Communist Party before the end of the civil war. During World War II he became an advisor to the Home Guard. 

British Battalion Commanders in the Spanish Civil War

Wilfred McCartney
Tom Wintringham (1898-1946)
Jock Cunningham
Fred Copeman