In July 1916 Derby returned to the government when he was appointed Under-Secretary of State for War by H. H. Asquith, and in December 1916 he was promoted to Secretary of State for War by David Lloyd George. In this position he was a strong supporter of the Chief of the Imperial General Staff Sir William Robertson and of the Commander-in-Chief of the BEF, Field Marshal Haig. Haig privately had little respect for him, writing to his wife (10 January 1918) that Derby was "like the feather pillow, bear the mark of the last person who sat on him" and remarking that he was known in London as the "genial Judas". Robertson's biographer writes that during the crisis over Robertson's removal Derby "made himself ridiculous" by asking everyone, including the King, whether or not he should resign, and then in the end not doing so, only to be removed from the War Office a few weeks later.