This article is too damned short, Marine! You will help Gruntipedia by so it will fit the screen, fool!
The United Nations Space Command Defense Force (or just UNSCDF or the ones that can't defend a grain of sand.) is not the defense force for the Earth or you, but the defense force for the UNSC. They protect the UNSC from wide spread attacks like bombs, terrorist attacks, and criticism. Wait, not criticism. That's what the suppressing police is for...I mean, the UNSCDF is the best defense force ever because it has the the best of the best and mutants. The UNSCDF consists of many, many military groups. Fear the military groups. Live with the military groups. Participate in the weekly orgies. Uncle UNSC wants you!
According to the UNSCDF, the United Nations Space Command Defense Force has fought many wars and, at the end, were victorious, no matter what happened in the middle. The UNSCDF has fought in Halo 1, Halo 2, Halo 3, Onyx, Reach, your mom's bedroom, even in Earth. Now, do you see anything wrong with those places after the war? No. This article has been approved by the United Nations Space Command Defense Force.
The UNSCDF has branches. It's a happy tree.