NO MILATARY puts its entire assets into a war !
Except when it just happens to be a war that, if lost, could spell the death of billions and the destruction of two species.
Or you are gooing to come up with some cannon evidence that the entire GTVA fleet was composed of nothin more then 7 or so destroyers and a dozen corvettes because that is insane.
You seem to be forgetting the sheer scale of the conflict. To start, the NTF rebellion likely took the majority of the fleets stationed in Sirius, Regulus, and Polaris through defection and surprise attacks, leading to the GTVA's loss of three fleets alone. The heavy casualties sustained in Deneb and Epsilon Pegasi are canon evidence of the losses sustained by the GTVA. For the NTF, the Colossus and the gauntlet of blockades en route to Gamma Draconis were both factors in destroying significant portions of the fleet.
So, let's add this all up. The NTF lost approximately 9 destroyers and about 6 or so corvettes. The GTVA lost 75% of the 6th Fleet, sustained heavy casualties in Deneb, and met fierce resistance from a two-pronged offensive in Sirius. With the canonical NTF casualties, the total is at about 108,000 dead, and those are just the destroyers and corvettes mentioned in briefings or seen ingame, and does not include the countless cruisers, convoys, pilots, and marines.
The GTVA is already known to have lost 85,000 in EP, and, when added with the casualties in other theaters of the civil war, likely lost well over 100,000 as well.
By the end of the civil war, the GTVA was fighting without the strength of the Regulus, Polaris, Sirius, and Epsilon Pegasi fleets. Because many of these fleets were short jumps away from Capella and the Shivan front (namely Polaris and Epsilon Pegasi), the GTVA likely had to call up help from both the Vasudans and other GTVA fleets throughout the galaxy.
The Shivan incursion was very likely even more costly for the GTVA. Multiple warships fighting the Ravana alone were lost, as well as two destroyers and the Colossus to the Sathanes alone. Add to this that the GTVA had sustained over 100,000 casualties in Capella when the plan to collapse the jump nodes was finally launched. The fierce Shivan attacks at the Vega and Epsilon Pegasi nodes likely cost thousands of casualties as well, not to mention the sizeable fleet left behind in Capella at the time of the supernova.
So there you have it. 100,000+ in Capella, 100,000+ in the civil war (not counting the genocide of the Vasudans), and 100,000+ for the NTF leads to well over 300,000 combat deaths, at least 13 mentioned destroyers lost, and four fleets essentially lost.