A Bolo is a fictional type of artificially intelligent superheavy tank. They were first imagined by Keith Laumer in the short story "Combat Unit" in 1960. They have since been featured in science fiction novels and short story anthologies by him and others. While stories are partly set in the near future, most take place in the 27th to 33rd century or even later. The fictional universe of Bolo stories is populated by alien races, which forced humanity and human colonists on distant planets to defend themselves with a large military.