Mobilization is the act of assembling and readying military troops and supplies for war. The word mobilization was first used in a military context in the 1850s to describe the preparation of the Prussian Army. Mobilization theories and tactics have continuously changed since then. The opposite of mobilization is demobilization.

Mobilization became an issue with the introduction of conscription, and the introduction of the railways in the 19th century. Mobilization institutionalized the mass levy of conscripts that was first introduced during the French Revolution. A number of technological and societal changes promoted the move towards a more organized way of deployment. These included the telegraph to provide rapid communication, the railways to provide rapid movement and concentration of troops, and conscription to provide a trained reserve of soldiers in case of war.