Before the War
Before the gangs began to attack each other, the Cubans went on a rampage against the Haitians and murdered a Haitian Gang Lord. However, the Haitians are unaware that the death of the gang lord was caused by the Cubans, so Avery Carrington sends Tommy Vercetti, whom he hired earlier before, out to kill the new gang lord of the Haitians while disguised as a Cuban gangster.
Tommy heads to the funeral parlor in Little Haiti and has the Haitians see him before he chases the hearse down. As the hearse rushes away, Vercetti follows behind and attacks the car with everything he has, such as shooting the vehicle or ramming the vehicle off of the road. After taking enough damage, the new gang lord exits the vehicle and begins to attack Vercetti with his M4 rifle. Tommy attacks back and eventually guns the gang lord to the ground. After slaying the gangster, Vercetti makes his way out of Little Haiti, which marks the beginning of the war.
Start of War
Since Vercetti had the Haitians notice him, and notice him kill the gang lord down while disguised as a Cuban gangster, the Haitians then realize that the Cubans were behind the first slaying, and declare war against the gang. During the time that the war occurs, Haitian and Cuban gangs can be seen spawning in each other's territories (Haitians in Little Havana and Cubans in Little Haiti).
As the sides fight each other, Vercetti receives a call for Cuban leader, Umberto Robina, who employs Tommy to do some work for him. Upon arriving at the Cafe Robina, Umberto begins to mock Vercetti, thinking that he isn't a man, but allows Vercetti to prove to him that he can handle a boat properly while another member of the Cubans gang watches him. Then, Robina has Vercetti go with his Cuban boys and steal a van, filled with drugs, from the processing plant, then ambush a drug deal between the Haitians and the Streetwannabes. After completing the tasks, Umberto has Tommy leave for a while while he thinks of a way to eliminate the Haitians. In the meantime, Vercetti heads to Auntie Poulet's place and does a few tasks for her.
Vercetti recieved a call from Haitian leader Auntie Poulet earlier on in the game, telling him to come to her home in Little Haiti for some more work. Since Poulet already knowns that Vercetti already has a tight relationship with the Cubans, she drugs him in order for Vercetti to preform her tasks for her, which all involve working against the Cubans. She has Vercetti obtain three breifcases for her before the Vice City Police Department obtain them from her. Then she has Vercetti destroy three of the Cuban's boats with an remote-controlled aircraft, equipped with the ability to drop bombs, then snipe dead some Cuban gang members, who are engaged in a fist-to-fit fight with the Haitians, which occurred not far from her home. After preforming all her tasks, Poulet tells Tommy that he's done working for her, and wishes for him to not return to Little Haiti.
In the meantime, Umberto comes up with an idea on how to defeat the Haitians once and for all, which is to destroy their large maufacturing plant. Umberto has Vercetti take Pepe to meet his friends in Little Haiti after finding a Haitian gang car. After meeting, the Cubans head towards the factory and enter the grounds. Realizing that its a Cuban ambush, the Haitians take action and attempt to stop Tommy and the Cubans with their Tec 9 handguns. However, they're all killed by the Cubans and Tommy heads into the building and plants the bombs. After planting the bombs, Tommy and the Cubans retreat away from the building and watch the building being destroyed by the bombs.
End of War
Due to the destruction of the Haitian Drug Factory, the gang war resulted in Cuban victory, and the gang war calms between the two sides. Although the Haitian's business was destroyed by the Cubans, the Haitians seek revenge against Vercetti, attacking him if he should return to Little Haiti.