Per the comments on the regimental system. The British Army has always had a regimental system which was administrative and esprit oriented. Each of the regiments had an adminstrative and training headquarters located in Great Britain. Depending on the war, the regiments would raise various numbered battalions, which would be assigned to brigades. The brigades weren't permanent organizations. The brigades were assigned to divisions, which also weren't permanent organizations. As wars and campaigns came and went the higher numbered battalions and the brigades and divisions came and went also. The US Army and Marines started off with a permanent regimental system. Occasionally a regiment was renamed, but depending on the war the regiments were designed to at least last during the duration of the war. While the number of troops, companies and batteries would vary during the centuries, normally there were twelve of each to a regiment. During a war the regiments normally served with all companies, typically organizind twelve companies into 3 battalions or squadrons(cavalry) During the Civil war Or the War Between the States or even the War of Northern Agression, the US Army grouped regiments into brigades, which usually were permanent during the war. The brigades were then organized into divisions\corps\grand armies, but these weren't very permanent. Brigades were often swapped between the divisions. Some states refused to send replacements to their regiments, raising new ones instead. Those states often merged older regiments with few men left into newer regiments. The US Army always sent replacements to its regiments as the number of regiments was closely controlled by Congress. After the Civil war, the brigades\divisions\corps etc were disbanded and never re-organized as such with the old names. During the First World War, all regiments were formed into permanent Divisions\Corps\Armies During the Second World War the Army found that regiments weren't always the best size of men to deploy. They might not want to deploy twelve companies with no attached artillery. Yet a brigade might be too big for a job. They formed task forces and regimental combat teams. After Korea, the army redesigned all combat units, effectively eliminating the regiment of twelve companies with battle groups of 5 companies. This only lasted about 5 years, then the Army went to what amounts to the existing system. The historical Divisions were maintained. The 3 regiments were replaced with 3 brigades. Each brigade had 3-4 infantry/armor battalions, an artillery battalion, and various other companies/battalions depending on its mission. To maintain esprit and not lose the history of the old regiments, each battalion was assigned a name& number relating to its predecessor regiment. Thus the First Cavalry Division has various Cavalry battalions/squadrons such as the 1st battalion Seventh Cavalry. The brigades these battalions belong to can easily change but the battalion tends to keep its name and traditions. About every 20 years the Army does change this organization, but in general, the Army is comprised of Battalions and Divisions. There's no Regimental headquarters as such, except for a few Armored Cavalry regiments. The Marines continue to maintain permanent regiments, assigned to permanent divisions. However their regiments are broken down into permanent battalions, so you can get the 2nd battalion, 1st Marine regiment Confusing. And one really needs to know what year in time, in order to know what comprised the 1st battalion of the 1st Infantry regiment. Don Conrad