Shout At The Devil - Wilbur Smith

They couldn't be anymore different: an earnest young Englishman named Sebastian Oldsmith and an Irish American adventurer named Flynn O'Flynn who never encounters a rule he doesn't break. Fate brings them together in Zanzibar. A sadistic German turns them into allies, then into warriors.
From the moment Rosa O'Flynn lays eyes on Sebastian, Rosa finds the man she would love forever--never mind what plans her father has for her. But imperialism is shaking Mozambique, where O'Flynn is the craftiest, fiercest beast in the jungle. And when Rosa and Sebastian lose what is most precious, they join a band of rogues, natives, wanderers, and hunters to start their own war against an enemy who has nothing to fear--and everything to lose...