More info on the RCTs I found in an older file. I've also been looking through the Historicals and there is more interesting info there as well.
Terran RCT (House Cameron, destroyed during initial Amaris Coup)
277th Light Horse Regiment (destroyed)
138th Hussar Regiment (destroyed)
118th Dragoon Regiment (destroyed)
593rd Striker Regiment (destroyed)
1st RCT (House Marik, 1 unit survived, departed on Exodus)
42nd Hussar Regiment (destroyed Hegemony Campaign)
75th Light Horse Regiment (destroyed Periphery Uprising)
138th Dragoon Regiment (survived Exodus)
195th Royal Light Horse Regiment (destroyed Periphery Uprising)
2nd RCT (House Steiner, Paget’s War Ponies and the 12th Star Guards)
25th Striker Regiment (survived, joined LC)
85th Light Horse Regiment (destroyed nuclear strike, Detroit pre-Amaris Coup)
147th Dragoon Regiment (destroyed surrounded, Detroit pre-Amaris Coup)
1111th Royal Light Horse (destroyed surrounded, Detroit pre-Amaris Coup)
3rd RCT (House Kurita, Eridani Light Horse)
71st Light Horse Regiment (survived, joined FWL)
151st Light Horse Regiment (survived, joined FWL)
19th Striker Regiment (destroyed Hegemony Campaign)
21st Striker Regiment (survived, joined FWL)
4th RCT (House Davion, 2 units survived, departed on Exodus)
255th Light Horse Regiment (destroyed Hegemony Campaign)
111th Dragoon Regiment (survived Exodus)
55th Royal Light Horse Regiment (survived Exodus)
247th Dragoon Regiment (destroyed Hegemony Campaign)
5th RCT (House Liao, 1 unit survived, 1 unknown)
1003rd Light Horse Regiment (survived Exodus)
1010th Light Horse Regiment (destroyed Hegemony Campaign)
982nd Royal Striker Regiment (destroyed Periphery Uprising)
997th Striker Regiment (unknown, MIA circa 2766 to 2769)
Terran RCT (FM SLDF)
The 277th Light Horse Regiment, 138th Hussar Regiment, 118th Dragoon Regiment, and 593rd Striker Regiment are permanently assigned to the Terran regimental combat team. This four-regiment unit acts most commonly as an aggressor for I Corps’ divisions, but often cycles offworld to Mars and Venus for duty. Unlike most RCTs, which are made up of mostly light horse regiments, the Terran RCT is built of several classes of regiment to add variety to its tactics.
2nd RCT (House Steiner Sourcebook)
Inspired by what the large military exercise of 2651 had taught, the Star League now announced the formation of Regimental Combat Teams, groups of four combined-arms regiments to be stationed at strategic points around the League. The Second Regimental Combat Team, formed from two Striker Regiments and two Light Horse regiments, came to be headquartered on the Lyran world of Main Street. Soon nicknamed 'Paget's War Ponies' after the unit's commanding officer, the 2nd RCT became a much-admired model for the local LCAF.
The departure of the 2nd RCT from the far reaches of Coventry Province created a military vacuum there. A group of bandits decided to exploit the situation with a raid that devastated the Lyran world of Main Street, the former home of the 2nd RCT. In response to the bandit attacks and the general tensions throughout the Star League, the Archon placed the LCAF on general alert.
2nd RCT (FM SLDF)
Though it is listed merely as a “member of the Second RCT,” the reality is that the Twenty-fifth Striker Regiment is currently also the entirety of the Second RCT. The RCT was dispatched to the sparsely populated Detroit system to investigate rumors of weapon stockpiles. It was completely unprepared for a full division of Taurian rebels. The Eighty-fifth Light Horse was erased in a nuclear strike, while 147th Dragoons and the 1111th Royal Light Horse died as they were outnumbered and surrounded. Their death did allow the Twenty-fifth to fight its way through enemy flankers to escape to call in reinforcements. They have since returned to full strength, but the rest of the Second RCT remains empty for now.
4th RCT (FM SLDF)
The four independent regiments—the 111th and 247th Dragoon Regiments, 255th Light Horse and Fifty-fifth Royal Light Horse—make up the Fourth RCT. Under the command of Lieutenant General Regis Colson, the Fourth RCT is the lead unit on anti-bandit operations. Working with SLIC assets, Fourth RCT has surprised several bandit groups either during their raid, or at the bandit’s base. This success has made tracking Fourth RCT a prime concern for both bandits and pirates, allowing LIV Corps’ Ninetieth Dragoon Regiment to make a few surprise raids along the border.
5th RCT (FM SLDF)
In pursuit of the pirates and bandits plaguing the Capellan border, the four regiments of the Fifth Regimental Combat Team have been operating independently nearly non-stop for almost four years. In this time, the RCT has become a team in name only—despite sharing a homeworld with LXXI Corps and one another, the regiments have grown distant in both tactics and esprit de corps from one another. The recently-returned 1003rd Light Horse Regiment is the most experienced of the RCT, having fought three company sized bands in the past eighteen months. The 1010th Light Horse Regiment and 997th Striker Regiment are currently training against members of the Sixtieth Jump Division, though the two regiments expect to go their separate ways once they are released to their hunts. The 982nd Royal Striker Regiment is currently broken into battalion sized task forces, jumping from unnamed star to unnamed star within the Capellan Confederation. Seventh Army has noticed Fifth RCT’s inability to function as a combined unit. General Huong informed General Janssen that if he doesn’t recombine the RCT and use it as designed, he would consider the Fifth RCT available for reassignment to another corps.