The Front Line is the first mission of Metal Slug: 2nd Mission. Seven prisoners exist in this stage.
Gimlet and Red Eye travel the mission on the same path, however Gimlet (and Tequila) uses the Slug Sub while Red Eye uses the Slug Flyer in the mission's second section. Destruction of the Slug will lead to a small detour with Gimlet and Red Eye using the Drop Pack and Emergency Boat respectively. The third section uses the SV-000, but no mission divergence occurs when the Slug is destroyed. The mission's boss is Big Bertha.
|The top brass, tickled pink with PF squad's success in First Mission, plans to deploy squads all over the world.|
|Yet squad members, sent out on faulty info that too often led to dead ends, soon lost faith in Intelligence HQ. At this time, the rebel strike force "PHANTOM", led by Commander Makuba, resumed activities.|
|Skeptical of IHQ info on Makuba, the PF Squad sends cadets to the site.|
|XX, XX The Mission Begins. It's my first one. A number of rebel holdouts continue their resistance. Now, if I don't cross enemy lines, the unrest will never end.|
|Independent of the PF Squad, IHQ creates its own squad of double agents and special ops agents that'll later form the squad known as "Sparrows".|
|Spies within this squad then leaked this mysterious info: UFOs were seen at the rebel base. Later, more wild info as sightings of alien visitors at the rebel base were also included in there.|
|Not to be trifled with, IHQ sends special ops agents to confirm the reports.|
|XX, XX. This is my first mission since I joined the special ops squad. And yet, I can't believe I'm off to confirm reports of flying saucers and little green men. I don't think it is necessary to plunge into a bunch of rebel holdouts to check such weird info. Regardless, I must cross enemy lines and get the ball rolling.|