20XX A.D. After years of preparation, General Morden begins his coup d'etat to seize control of the world from its current leaders.
With his blitzkrieg of insurgency carried out by his forces and the support of effective sympathizers propping him up throughout the world, the major cities of the world fall into his grip within a mere week after Morden gave the order to attack and lose all capabilities to resist.
The world is lost in a collective bat of the eye.
In the face of the General's revolt, a small band of survivors from the quickly overrun Government Forces begin to form a resistance and struggle to rebuild their troop strength while biding their time till the opportunity to stop Morden arrives.
Then, disaster strikes. The secret factory of the resistance shatters into pieces with a deafening blast. An attack by the General's revolutionary forces! They have finally been discovered! This truly lops off the head of the resistance's vanguard force that still lack sufficient military strength, and leaves a number of new, all-purpose METAL SLUG tank prototypes smoldering in the ruins or ready to fall into enemy hands.
There can be no hesitation now.
The Special Forces Squad Peregrine Falcons (a.k.a., PF Squad) of the Government Forces receive their orders:
"Pinpoint the General's Revolutionary Force's lead position with a small unit and take it out! The stolen METAL SLUGs must be returned and kept secret or, if no other options are available, be destroyed."
The two soldiers selected for this mission, Marco and Tarma, know they must not fail. The battle to subdue the General waged by these two alone begins...