MACO

Military Assault Command Operation, commonly abbreviated as "MACO"
Existed as a part of the United Earth Military during the 2150s
As of 2153, MACO tactics and technology were two to three years more advanced than those of Starfleet
Their combat expertise was initially limited to simulations conducted on Earth
A detachment of troops was assigned to the Enterprise for a mission into the Delphic Expanse in 2153
Following the foundation of the United Federation of Planets, the organization was disbanded
Personnel were offered Federation Starfleet commissions on a discretionary basis