Ultima Thule Invasion Earth

Don't call him Billy the Kid.

Lt William Bonney, LT for short, leads a ragtag group of soldiers on an impossible mission to save earth from invading aliens.

Book four in the Invasion Earth Series that includes:

Beachhead

Bridgehead

Lodgement

Ultima Thule

Infiltrate

Snakebit

Riki Tik

Defilade