In May 1961, President John F Kennedy called for a NASA program to send a man to the Moon. But the US Army had already undertaken a classified feasibility study that was much more ambitious in scope than a mere Moon landing. Dubbed “Project HORIZON”, the Army’s plan called for a permanently-manned lunar outpost that would be powered by nuclear reactors and armed with spy cameras and nuclear weapons. By permanently occupying the Moon, and more importantly by getting there before the Soviets did, the US could lay claim to ownership, and controlling the Moon was seen as one of the vital keys to winning the Cold War. This declassified Project HORIZON report is a revealing look at the state of the technology available before the first human space flights, and how it was assumed they would develop over the short term. Many of the ideas first considered in this report have found their place in later space projects—including future Mars landings. Illustrated.