Raúl Marín is an elite navy commander of the FND whose family was killed by guerrillas. Blinded by revenge, he leads the very first insurgency formed by remnants of FND in the wake of Castillo regime downfall and retaking control of the province of Noventarmas. During the insurgency he controls the naval activity of Yara from FND Special Forces Base, since the FND Heavy Gunner "boss" Sergeant Iglesias in charge of the base was already dead at that point.
Just like the other insurgent leader Juaneta Cuda, Raúl Marín combat style is the same as FND Vanguards, charging forward for close quarter combat using the sawn off version of 1887 just like FND Engineers and FND Special Forces Snipers. He uses incendiary grenades unlike the of previous games who used smoke grenades. He only fight on foot when he is unable to use the tank, otherwise he would quickly jump inside the tank as soon as possible.
Raúl Marín is the brother of Crash Marín, another insurgent leader. Raúl Marín supposedly served under Admiral Aña Benítez since she was in charge of the navy. It's unknown whether Raúl Marín literally held Commander rank or just simply had significant forces in the navy under his command.
Fittingly, Raúl Marín is the literal vanguard who led the charge and started the first insurgency which inspired other insurgents.