Trotsky and the government responded with a full-fledged mobilisation, which increased the size of the Red Army from fewer than 300,000 in May 1918 to one million in October, and an introduction of political commissars into the army. The latter had the task of ensuring the loyalty of military experts (mostly former officers in the imperial army) and co-signing their orders. Trotsky regarded the organisation of the Red Army as built on the ideas of the October Revolution. As he later wrote in his autobiography: