The United States has developed a new way to deliver naval mines; by attaching a JDAM glide and satellite navigation kit to naval mines designed to be dropped, like dumb bombs, into shallow water. The JDAM mine can glide 70 kilometers thus avoiding many enemy air defenses.
Mines are simple armed autonomous drones, really. Stationary, but still killer, robots.
But they have worked well for over a century. Hopefully we pay attention to clearing them and laying them.