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 1757 Invasion of Hanover