Earth's Fury. Obsidiar Fleet, #4

Earth's Fury. A gun to shatter a god ship. The human Confederation has provided unexpected resistance to the Vraxar invading forces, but now the price must be paid. The mighty enemy warship Ix-Gorghal has discovered the location of humanity's populated worlds and its arrival in New Earth orbit promises death for the billions living there. At first, it seems the invaders will have everything their own way.
They send in troops and deploy a ring of satellites to isolate the planet from the main comms network. After that, it should all be plain sailing.. On the New Earth Tucson military base, there are personnel who will never accept defeat - men and women who will keep fighting even when the cause seems lost. Lieutenant Eric McKinney is one of them. An unexpected message from a lone fleet warship high above the planet sends him on a mission to rescue the only man on New Earth with the activation codes for two unfinished warships on the Tucson base - the battleship Ulterior-2 and an experimental gun called Earth's Fury.
Fleet Admiral John Duggan is the man with the keys. He's got a mission of his own and if it succeeds, it will ensure total annihilation for both sides. Duggan can see no other way out. Meanwhile, Captain Charlie Blake has other problems. In order to help the people of New Earth, he's forced to defy orders, putting his life and his future in jeopardy. He's one of the few men with the skill and audacity to get Earth's Fury into orbit - assuming it will even fly.
It won't be easy. The Vraxar are a cruel and unpredictable foe, and at the first sign of a threat, they will surely destroy New Earth without hesitation. Earth's Fury is a high-action science fiction adventure and the fourth book in the Obsidiar Fleet series.