Project DEFENDER is a large construction by humanity created during the Galactic War. DEFENDER is a very large weapon in space that Humanity hopes will be used as means to destroy the Reapers before they can complete their destruction of all life in the galaxy.
DEFENDER's effects on all other life, however, is unknown. It is speculated that it could kill many other people when fired, but Human officials announced to the other galactic races that they will "have to hope for the best."
DEFENDER was fired in January 2013 at the hands of Microsoft Sam. The construction charged with green energy, releasing the first bout in a huge wave, destroying the Reapers in and around the Sol System. DEFENDER then took the last of its energy and shot it deep into space, impacting on a planet in another system. The beam deflected off the planet and into another, the impact generating another wave that cleansed the Reapers from this system as well. This energy ricocheted around the Rofl-Way galaxy for an undetermined amount of time. What it did do however was destroy the Reapers, saving the galaxy.