Vance-Mendez War

The Vance-Mendez War was a giant war in Grand Theft Auto: Vice City Stories fought between the Vance Crime Family and the very powerful Mendez Cartel. The people involved in the war were Victor Vance, Lance Vance, Louise Cassidy-Williams, Phil Cassidy, Umberto Robina, Armando Mendez, Diego Mendez, Ricardo Diaz, Reni Wassulmaier, and Jerry Martinez.

Before the War
The feud started when the Vance Crime Family stole the shipment of drugs belonging to the Mendez Cartel, which they believe belonged to Jerry Martinez. When Janet Vance, and his boyfriend stole the cocaine from his sons, the Mendez organization begins to send death threats to the brothers if they do not return their cocaine from them. The Vance's begin to work for them and telling that Martinez was an undercover cop and he stole the coke from the Mendez brothers using photos taken by Victor when Martinez' begins to turn states. Later, the Mendez' hires Victor to take over a site as a front to increase the flow of drugs into Vice City; kill the drug dealers to eliminate the competition; and stealing the container from the compound. The Vance also begin to work for Gonzales and Diaz' Gang, which were the rivals of the Mendez Cartel, with the help of Reni Wassulmaier.

The War Begins
Lance and Victor went to the Mendez Mansion for some work for the Mendez' brothers, telling them that they are free, as long as they leave Vice City and give their assets to them, but they refused and betray them and send to Viceport but narrowly escapes execution. After this, the Vance brothers cut their ties with the Mendez' brothers and declare war against them.

Lance, with the help of Umberto Robina and Phil Cassidy defend Victor Vance's businesses; Lance and Victor begins to work for Ricardo to help them bring down Mendez' organization, saving Reni Wassulmaier from the grip of Diego Mendez' goons and helping Reni escape Vice City. Lance also informs Vic that Louise will be kidnapped again but he was tricked by Martinez' and took his money.

Ending of the War
In retaliation for the destruction of his bonds, Armando kidnaps Louise and lures the Vance brothers in a trap. In an attempt to rescue Lance and Louise, Victor kills Armando but Louise is killed by Armando. Diego later went into exile in a compound in Downtown. Victor hunts him down by stealing a helicopter with the help of Phil and using it against Diego. He is eventually shot down, but survives and make it to the compound and after slaughtering many of Diego's man, finally confronts Diego in the compound's roof. There they are joined by Jerry Martinez and a final confrontation starts where Victor manages to kill Jerry and Diego for good. After that, the Mendez Cartel crumbles and the Diaz' Gang rose to power in the city, alongside Vance Crime Family.

Trivia

 * Though there was a war raging between the two factions, no Mendez goons appear outside of their territory.