After the drop on Typhon, the Fusiliers, led by Sergeant Eszo, attempted to meet up with Captain Cole and the 3rd Militia Grenadiers at an IMC Interstellar Beacon that would allow them to call for aid. However, their path necessitated travel through a Water Reclamation Facility controlled by the IMC and Apex PredatorKane. Ultimately, the soldiers were decimated by the newly-deployed Stalkers before the arrival of Pilot Jack Cooper. Ultimately, Cooper would continue through the facility, leaving the Fusiliers to themselves. Presumably, they were hunted down and destroyed by IMC security forces.
Assuming that the Fusiliers are a Company-level unit (See here for details), being led by a Sergeant implies that all Majors, Captain and Lieutenants in the Fusiliers were killed in the fighting prior to Jack Cooper's awakening in BT-7274.