I'm trying to remember and locate an old SF short story. It's set in the future and describes an unending war between humanoid robots who are taking over the conflict from humans. The humanoids on one side are all identical. Some of the robots are tiny to infiltrate enemy bases. There might be a connection with the Terminator films. I read it in an anthology in the 1980s but it was written probably in the 1960s. What is this?