I thought the Army or national guard would be that main force if america was ever invaded not the Marines. Never played the first that may be a reason I an confused

If it was Army it would be suicide.

I'm pretty sure the army would be the main force, however, I pretty sure the marines wouldn't just be sitting on the sidelines

No the army is the force that supports the marines in their offensives but the arrmy is manly used for defencive positions becouse of their large amounts of troops.

The Us Army and The Marines, a force worth recognizing.

I'm pretty sure the army would be the main force, however, I pretty sure the marines wouldn't just be sitting on the sidelines O yea they would be fighting I just thought the army would be the bigger force as in the people fighting an evacing the civvies not the marines

I'd think that if America was invaded by Aliens, it wouldn't be just one particular group of people aiding in it's defense... it would be the lot of them. Pewpew!

the ARMY would be doing the S&R stuff, saving and protecting civilian evacuation, meanwhile, the Marines would be doing the direct combat against the aliens with you along side to help fight

Maybe it's a sign of how thinly stretched the US forces are. Just showing that they have very little in terms of self defense left that they have to use their invasion force.

australians have not such a big army but really skilled
and well trained!