Within the U.S. Army, generals are at the top of the chain of command. Within the Army general officer community are four ranks of progressively higher authority. They start at the brigadier level (one star) and top out at general itself (four stars). In between are the ranks of major general and lieutenant general. The Army commands they lead and the responsibilities they have are commensurate with their pay grades.
A brigadier general in the U.S. Army holds the pay grade of O7 (on a scale of O1 to O10). Depending on his specialty, a brigadier serves as deputy to the commander of a division-sized unit. This means he's second-in-command of a unit containing 17,000 to 21,000 soldiers. He's usually the officer in charge of all planning and coordinating activities. Brigades (3,000 to 5,000 soldiers) that don't belong to a division are commanded by brigadiers.
An Army major general holds the pay grade of O8. Given that he commands division-sized units, his duties and responsibilities are vast. Within his division exists seven brigades. These include aviation and artillery units. When not commanding these large units, he may serve in staff positions at the Pentagon. Additionally, major generals also are found working in specialized organizations such as the National Security Agency (NSA). They may also serve as leaders of doctrinal development commands.
A lieutenant general holds the pay grade of O9. He often commands a corps-sized unit of from 20,000 to 45,000 soldiers. In addition, he can be found holding high-ranking positions at all major U.S. military commands. For example, the deputy commander of U.S. Southern Command (USSOUTHCOM), a unified (all-service) combatant command, is a lieutenant general. His duties include responsibility for all U.S. military activities carried out in Central and South America.
An Army general holds the pay grade of O10 and is the highest-ranking of the four general officer ranks. The military commander of the U.S. Army is a general. Generals command major responsibility areas such as U.S. Central Command, with responsibility for the Middle East. In addition, Army generals are periodically named to be chairman of the Joint Chiefs of Staff.
All Army generals hold a great deal of responsibility. By law, the Army can only have approximately 302 of the them at any one time. An Army general is rated O-10 on the pay grade scale. In January 2013, an O-10 with 20 years in service earned $15,913.20 per month, according to the U.S. Bureau of Labor Statistics. Lower ranks, at grades O-7 to O-9, earn between $8,182.50 and $13,917.60 per month, depending on rank and time in service.