What is Mobilization?

Legal Definition
Mobilization, in military terminology, is the act of assembling and readying troops and supplies for war. The word mobilization was first used, in a military context, to describe the preparation of the Russian army during the 1850s and 1860s. Mobilization theories and techniques 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 forces that was first introduced during the French Revolution, and that had changed the character of war. A number of technological and societal changes promoted the move towards a more organized way of assembling armies. 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.
-- Wikipedia
Legal Definition
Until the completion of the contract transfer to a construction site of a contractor's physical and manpower resources.