So I re-read Shattered Fortress and I came up with a list of all destroyed Republic regiments/battalions, where they were destroyed, when, and by who.
Hastati Sentinels Regiments
7th Hastati (Heavily damaged on Callison, Arianna Zou taken bondswoman by Clan Wolf)(Wolf Empire, 3150)
10th Hastati (Defeated on Wing, retreated) (Wolf Empire 3150)
11th Hastati (Defeated, drove to ground on Thorin) (CJF 3151)
13th Hastati’s (1 Battalion on Epsilon Indi, 1 Battalion damaged on Bryant, remaining Battalion mauled on New Home) (House Liao, 3149)
15th Hastatis (defeated on Castor) (Wolf Empire 3150)
Principes Guards Regiments
3rd Principes (1st Battalion on Chertan, hurt on Marcus) (Wolf Empire 3149, 3150)
10th Principes (Partially destroyed on Shiloh) (Wolf Empire 3150)
11th Principes (Destroyed/absorbed on Alula Australis, fought CJF on Thorin) (Wolf Empire 3151)
12th Principes (Defeated on Phecda, retreated, destroyed on Pollux) (Wolf Empire 3150, 3151)
14th Principes (1 battalion lost on Hall, 1 battalion lost on Outreach) (House Liao 3149)
13th Principes (1st battalion lost on Episolon Eridani, 2nd battalion Lost on Terra Firma)(House Liao 3149)
15th Principes (Destroyed/Absorbed on Denebola) (Wolf Empire, 3150)
Triarii Protectors Regiments
8th Triarii Protectors (Defeated on Alhena, hurt on Marcus) (Wolf Empire 3149, 3150)
10 Triarii Protectors (Destroyed on Wing) (Wolf Empire 3150)
11th Triarii Protectors (defeated on Outreach, showed back up on Liberty)(House Liao 3149)
12th Triarii Protectors (Destroyed to the last on Garcrux) (3150)
13th Triarii Protectors (Defeated on Procyon, 3149) (House Liao)
Fides Defenders
1st Fides (Defeated on Shiloh, forced to retreat, destroyed on Graham IV) (Wolf Empire 3150)
2nd Fides (Defeated on Phecda, retreated, destroyed on Pollux) (Wolf Empire 3150, 3151)
4th Fides (Destroyed on Rigil Kentarus, fought alongside Clan Wolf) (Clan Jade Falcon, 3151)
5th Fides (Defeated on Castor) (wolf Empire 3150)
Republic Mercs
Aquamarines (Forced to ground on Formahault, 3150)
The Fidelis on New Earth surrendered en masse to Clan Wolf, and Paul Moon was seen meeting with Khan Alaric Ward
Just for completion's sake, here are the 2 "Army Groups" the ROTS used in Operation Eruptio, and then against Clan Wolf.
First Army Group
10th Hastati, Principes, Triarii, 1st Fides Defenders
2nd Army Group
11th Principes, 12th Principes, 12th Triarii, 2nd Fides Defenders
It really just doesn't make sense to me that Devlin Stone would throw away almost 75% of his military, leaving only 1 Hastatis Regiment (The 12th, which he was going to throw away on Northwind til Tara Campbell convinced him not too), and the Stone's Brigade on Terra. If his plan is to lure in Clan Wolf and try to merge the 2, surely he could have done so without throwing away all the other Brigades. Why not merge them all on Terra?