The Territorial Army, and therefore the brigade and the rest of the division, was mobilised between late August and early September 1939, and the German invasion of Poland began on 1 September, and the Second World War officially began two days later, after Britain and France declared war on Germany. Mobilised for full-time war service, the brigade was brought up to War Establishment strength in late October 1939 with large drafts of militiamen, men had been called up earlier in the year with the introduction of conscription in the United Kingdom and had just completed their basic training.