why is halo 3 odst called halo 3

why is halo 3 odst called halo 3. There are some references to why is halo 3 odst called halo 3 in this article. If you are looking for why is halo 3 odst called halo 3 you've came to the right place. We have images about why is halo 3 odst called halo 3. You can check it out below.