re: Is the Ka-bar a marine corp or army weapon?

It's a Marine Corps weapon. By that I mean it was officially adopted as the "combat knife" of the Marines back during WWII. Army soldiers can purchase it though. I'm sure they're sold in virtually every PX around the world. However, as far as a blade goes, the US Army currently issues the M9 Bayonet;



It's replaced the M7 Bayonet that was issued back in my day;



ETA: You can't really tell from this picture, but the M7 bayonet blade actually was lot longer than that of the Ka-Bar. The Ka-bar's blade is 7" long while the M7's blade was 11.9" long.