Looking for the short story about two men stranded on an alien planet that they thought only had a lot of stones/rocks. Turns out the stones/rocks are life forms that move very very very slowly (I think there's a group of white stones, and a group of red ones). One of the men starts to communicate and train the (red?) group, and uses them to mess with the main character. Then the main character realizes this, becomes friends with the (white?) stones and they start to fight a really slow war with their stone armies. Eventually they become stone as well, and later on when new explorers land on the planet, they think there are two statues of men on top of piles of stones. But actually they are just the two guys who have both been turned into the "stone" creatures and are continuing to fight a very slow war.
This short story was in an anthology of sci-fi stories at some point, would love to remember the name of the anthology as well as the story itself and author. I believe this story is pre-2000.