In 1898, during the Cuban War of Independence from Spain, a former U.S. Cavalry Captain, dishonorably discharged from the army, is a gun-runner. He, and other soldiers of fortune, renegades and outcasts, tempted by high profits, are defying the Spanish blockade of Cuba and are smuggling guns to the Cuban revolutionaries from Tampa, Florida. The ex-Cavalry Captain, Caleb Cash Adams, and his former Sergeant, Trasker, attempt to deliver a large weapon-shipment to representatives of the Cuban rebels but are told the weapons should be delivered straight to Cuba. Having no other customers for his weapons, Adams agrees but doubles his price. Fighting off a gang of hijackers they arrive in Tampa, where they are told to load the shipment onto an old river-boat, captained by an ex-Confederate Navy man, Capt. Sidewheel Jones. Adams and his men also notice that another gun smuggler and competitor, Clay Pike, is also loading a shipment of weapons on the river-boat. Adams and Pike are old enemies, going back to the days of the Indian Wars when Adams was in the Cavalry and Pike was selling guns to the Indians. During the sea voyage from Florida to Cuba, via Haiti, these two men often fight one another. To make matters worse, a passenger on the boat, Cuban revolutionary belle, Doña Isabella, who has been raising funds in Florida for the Cuban cause, is proving to be a bone of contention for the two American smugglers who are both attracted to her. The perilous voyage through a Spanish military blockade in the waters surrounding the Cuban island ends in Santiago where the weapons have to be unloaded on the shore and the payment has to be effected. However, things don't go as planned. The Spanish colonial troops are everywhere and the Cuban rebel General Maceo, who is supposed to pay the cash for the weapon-shipments, has retreated to the mountains. Pike wants to sell his weapons to the Spaniards while Adams wants to deliver them to Maceo. Things come to a head with a final showdown between the two rivals and their respective crews.