Have you ever tried to find a story whose title is a single letter without knowing the author? I'mI'm pretty sure the title was "T". It's about an alien race at war with humans. They decide to end the human race by destroying Earth before humans evolve. They send some humans through space and back in time to do the job. I
I think the humans have single letter names (A, B, C,etc etc) They have raised/cloned the humans just for the job and to save space in their ships they have only a head, a body, and 1one arm. Most don't make it.
The aliens don't know that there were 2 more planets in the past and they count the planets in from Pluto. One human hits a planet and completely destroys it and T hits a glancing blow and just breaks up his target forming the asteroid belt. I would like to read this story again but without the author I can't find it on the internet.