The Clone Wars is an unstable time. The Mandalore empire is stretching it's boundaries and confronting Republic forces when they attempted to stretch too far. The Mandalore have decided that the Republic was a worthy opponent to confront and so has put all of its' war efforts into crushing the Republic.

To defend its' borders, the Republic has mobilised all of its' fleets, and any other combat-worthy vessels that were to hand. They have also called a lot of retired personnel back into service.

So far, the war has only been going for one and a half years now, and is currently known as the "Mandalore War". The Mandalore vessels haven't been well catalogued as yet, but various unknown configurations of vessels have been sighted in the Danaan sector of space. This has meant that the Republic has had to place extra forces in the Danaan sector to contend with any unknown threat. Whether it is part of the Mandalore Empire or something else isn't known!