I'm quite surprised that no one mentioned the exceptionally well written series The Lost Fleet by Jack Campbell (AKA John G. Hemry).
The Lost Fleet comprised 6 novels which was essentially a massive fleet from the Alliance (good guys) was suckered into a huge ambush in the Syndicate (bad guys) home world system.
Bring in John 'Black Jack' Geary, a hero thought dead a century before who leads the fleet out of the jaws of defeat into a long and deadly trek back to Alliance space, all the while fighting attempts at mutiny, sabotage, and threats on a system wide scale.
Really worth checking out, believe me.
Chris