User blog comment:The Milkman/Indoctrination Theorists Say the Darndest Things, Part II/@comment-98.240.62.123-20121205183510/@comment-24174486-20121205185339

If you don't do Arrival, then the 103rd Marine Division gets sent in instead. The destruction of the system along with many of the marines halves the base value of the 103rd Marine Division war asset. It also slightly changes the beginning of ME3—Shepard is incarcerated for working with Cerberus rather than the destruction of the batarian colony.