Army of observation

An army of observation is a military body whose purpose is to monitor a given area or enemy body in preparation for possible hostilities.

Some of the more notable armies of observation include:
 * Third Reserve Army of Observation, a Russian army tasked to monitor the Austrian border in 1811 prior to the French invasion of Russia
 * The army of observation at Fort Jesup, Louisiana, United States, which monitored Texas' transition from Spanish to Mexican control, and to eventual independence
 * The Hanoverian Army of Observation which monitored the border prior to the French Invasion of Hanover in 1757