sentences:  The concept of establishing a long-term human presence on the Moon can be traced back to the late 1950s.The Lunex Project, conceptualized in 1958, was a US Air Force plan to construct an underground Air Force Base on the Moon.On 8 June 1959, the US Army's Ballistic Missile Agency (ABMA) organized a task force called Project Horizon to assess the feasibility of constructing a military base on the Moon.