West Cork Brigade's flying column and definitively made his name as a guerrilla commander at the Kilmichael Ambush on 28 November 1920. This was a turning point of the war, when a company of 18 Auxiliaries was wiped out at the cost three IRA killed. The British alleged that Barry's men had killed wounded and surrendering Auxiliaries and mutilated their corpses. This was a charge that Barry always denied, claiming that he had ordered that no prisoners be taken after the Auxiliaries faked a surrender resulting in the death of some of his men. Barry was hospitalised for a time after the Kilmichael action and martial law was proclaimed in County Cork and across much of the province of Munster in response. However, in December the column regrouped, attacking a number of police and military barracks in the West Cork region. In one such instance in February 1921, Barry's column attempted to launch an attack on the RIC Barracks in Rosscarbery, billeting at Burgatia House, which was owned by a Loyalist family, to avoid detection. However, a contingent of Black and Tans was sent out arrest them after being tipped off by a postman. After a brief firefight, Barry and his men were able to push them back and escape. The column, which was around 30–40 strong, dispersed shortly afterwards into smaller units and subsequently lost 11 men killed. Three men died in the Upton Train Ambush and eight more died in various incidents and encounters with British forces. In March 1921, Barry mobilised his largest guerrilla force of 104 men, divided into seven sections, and at the Crossbarry Ambush broke out of an encirclement of 1,200 strong British force from the Essex Regiment. At least ten British soldiers were killed in the action, along with three IRA volunteers including Brigade commander Charlie Hurley. In total, British forces numbered over 12,500 men in County Cork during the conflict, while Barry's men numbered no more than 310. Eventually, Barry's tactics made West Cork ungovernable for the British authorities except by military means. In the late spring and early summer of 1921, British forces mounted large sweeps of the West Cork area, complete with aerial surveillance and armoured vehicles, forcing Barry's column to spend much of its time "on the run" in mountainous terrain to avoid them. While they did avoid being encircled, they were able to mount only one more major