What you describe is called "In Media Res" (Latin for, "In the middle of things") and is one of my favorite storytelling techniques. The reader is immediately immersed in the action. They then become interested in the "backstory" (provided later), so as to make sense of the conflict (broadly defined) in which their minds have now become embroiled.
Quill
I knew there was a term for it. Thanks for your input @quillfire. I look forward to reading your story. I know it's going to be good.