User blog comment:Drkdragonz66/Call of Duty: Iron Wolf?/@comment-68.149.226.186-20120103005155/@comment-60.52.18.88-20120107083232

This wiki is the source.Go to http://callofduty.wikia.com/wiki/Call_of_Duty

And scroll to the bottom you will see Call of Duty Series just below the external links.

That's the source and probably the devs of IW and 3arc also agree that their stories are connected.If their stories are not connected,they should told us long ago.You can't just make your own rules.