One of the things i'm wanting to do is hammer out Operation Thresher into something coherent. All we know is that it was a direct assault on Vasuda via Antares.
I would suspect that the first part involved control of the Antares - > Vasuda node, which occured without much problem. It was the attack on the heavily defended Vasuda system that ranked up losses.
My take on Operation Thresher was the GTA trying a strategy of constant assaults against Vasudan outposts and vessels, 'leapfrogging' across the system in a fashion not unlike the blades of the eponymous thresher. GTA forces would bash through the node into Vasuda and break up into several separate units, each representing the different blades of a thresher. The first unit would attack the nearest outpost, the second would attack the next closest, the third the next, and so on until they ran out of spare units. They would time the attacks precisely so that by the time the furthest unit along is into their attack, the first unit would have finished their attack, rearmed and be ready to jump along to the next Vasudan outpost/fleet in the area. The idea being to blitzkrieg across the system, keeping the Vasudans on the defense and maximising confusion among their fleet.
Since it didn't work, obviously someone met more than they could handle or just plain cocked-up. After all, the strategy would be damned vulnerable if just one unit was held up or simply wiped out, as it would slow the whole advance and allow the Vasudans time to regroup and marshall their forces for a counterattack. That's how you could explain the high casualty rate: With GTA units spread out to all hell and back, a coordinated Vasudan counterattack would be able to pick them off without any trouble at all.
Oh, and I usually refer to this
whenever I mention something from the TVW era.