Metal Gear Solid – Portable Ops begins in 1970, six years after the bloody confrontation in the Russian jungle. Snake, now known as Big Boss, believed that his days of major conflicts were over. However, fate had other plans. He woke up to find himself imprisoned in a cell inside an unknown military base, his wounds still unhealed, and his mind searching for answers. How had the FOX Unit turned against the CIA, declaring rebellion and seeking a mysterious treasure known as the Philosopher’s Legacy—a black box that holds the keys to world domination?

Gene, the new leader of FOX, had carefully orchestrated this conspiracy and aimed to create an independent military nation—a rogue army of soldiers without a homeland. He wanted Naked Snake to be part of this revolutionary project, but he knew Snake would never submit so easily. While Cunningham, a sadistic intelligence officer, tried to extract secrets from him through torture, Snake was already planning his escape. Inside his cell, he met someone who would later become one of his closest allies: soldier Roy Campbell. Though alone, sick, and weak, Campbell had an unbreakable fighting spirit. Together, they devised an escape plan, relying only on their intelligence and determination. In the shadows of the San Hieronymo base, Snake began forming his own army, infiltrating enemy lines, recruiting loyal soldiers, and working to stop Gene before his mad dream became a reality.

Unlike previous Metal Gear games, Portable Ops was not just a classic stealth experience; it introduced an unprecedented strategic element to the series. Snake was no longer working alone—he had to build a complete team of soldiers, each with unique skills and abilities that could be used on the battlefield. The core gameplay revolved around recruiting soldiers instead of simply eliminating enemies or avoiding them. Snake could subdue and convince them to join his cause. Some soldiers specialized in combat, others in stealth, and some possessed medical or logistical skills to support the team outside the battlefield. Players could customize their squad for each mission, selecting characters based on the specific challenges they faced.

Before each mission, players had to assemble a four-man team to deploy into combat. The combat system retained the classic stealth dynamics, allowing Snake to sneak past enemies, hide in the shadows, and avoid detection by cameras and guards. However, the most significant addition was the ability to control multiple characters during a mission, offering greater tactical freedom. The game also introduced an online multiplayer mode, allowing players to form their own teams and engage in strategic battles against each other, making the experience even more challenging and exciting.

Compared to Metal Gear Solid 3: Snake Eater, Portable Ops was a revolutionary step in gameplay. While Snake Eater focused on stealth and survival in harsh natural environments, Portable Ops offered a more open-ended experience, allowing players to recruit soldiers, develop different strategies, and choose various ways to complete missions. The controls were also redesigned to fit the PlayStation Portable, with adjustments to map layouts and aiming mechanics for a smoother and more accessible experience. However, the most notable change was in storytelling. Instead of the full cinematic cutscenes that defined the series, this installment presented its narrative through illustrated comic-book-style visuals, giving the game a distinct artistic touch despite lacking some of the cinematic depth of its predecessors.