User blog comment:James12708/Why Exactly is Sheperd on Earth if Arrival Wasn't Completed/@comment-24174486-20121129213316/@comment-24174486-20121130123145

If you don't do Arrival yourself, the 103rd Marine Division gets sent in instead to deal with it. The marines are killed destroying the mass relay, resulting in the 103rd Marine Division war asset being reduced by 50 points.