Book of the Guardian Series by Ben Winston

John Aster has been a soldier for a long time, when he decides to retire, and once again become a normal human. His de-enhancement fails, and presents a never before seen situation, and an opportunity for his government. Especially since he picked the trouble spot as his new home.

John and his friends discover that his new home is being used as a spy base for humanity’s enemies. Will the group of friends be able to rid the planet of the aliens without them destroying it? Will the whole situation blow up and start another intergalactic war?

When a member of John’s old unit, the Temporal Guard, dies, The Last Mission is the term used for when his team mates escort their ashes to their final destination. However, the term is also used for a mission where a Marine losses his life. With the Tammerain trying to engage them in war, John and his team must escort one of their own on his ‘Last Mission’ but will it be their last mission too?