Why start a story with a horrific blast? Why not put it at the end, with lots of dramatic build-up to ka-blammo?
This is the most challenging question I imagine coming from a prospective agent for "Endgame." It's also the easiest to answer.
Set early in an inter-planetary war, the story centers on five soldiers charged with defending a fuel depot on an icy world. The thirty minutes of battle--tanks, sniper fire, mines, sacrificed youth--has been done before (a number of times) in movies. To me, the real story (the most compelling question) is what happens to the survivors in the aftermath of a Krakatoa-scale event? What can a sharpshooter heroine, June Vereeth, do when her group is stranded behind enemy lines, on an unlivable planet, with feisty wildlife, and with sworn enemies returning to the surface?
Right from the initial concept, that was the tale I wanted to write. I think you'll enjoy reading it, as well.