The political and military seeds for war were sewn long before he was imprisoned following the Moncada barracks debacle in 1953. At the time guerrilla warfare was virtually unknown, yet Fidel and his group had to devise a plan that would take a small band of poorly armed civilians and defeat an 80,000 man well-armed military backed by the world's biggest superpower. The charge was daunting, yet they forged ahead during those years leading up to their 1956 attack looking for any and all advantages over their vastly superior enemy. They knew that only through the added help of the local citizenry did they ever hope to win against Batista.
Fidel's strategy had always been political first and military second. He felt strongly that first and foremost was the need to get the public on their side and they spent a lot of time winning the hearts and minds of the people. Their treatment of the citizenry was always with the utmost respect and civility. They never stole nor abused the generosity of those around them. They always treated their captives with care and concern, tending to the wounded even when medicinal inventories were in short supply. Hemingway's novel about the Spanish Civil War, For Whom the Bell Tolls, played a pivotal role in their understanding of warfare and its effects on the surrounding population. They consulted it often during their trek through the Sierra Maestra mountains in the beginning.
By treating the enemy with respect, avoiding violence, torture and intimidation at all turns, tending to the wounded and infirm from both sides and ensuring that the civilian population was always properly recompensed for their services, Fidel made it possible for his group to win the hearts and minds of not only the civilians across the island, but of the very same army they were fighting. Where Batista used the ancient tactics of terror, torture, death and destruction to intimidate everyone they found in their path, the revolutionary forces commanded by Fidel followed international law and respected soldier and civilian alike. The only point where the death penalty became necessary was when members of his own forces were caught stealing from the local citizenry and were condemned under the rules of combat inside of a war zone. No case of prisoner mistreatment from that war has ever been leveled against Fidel and his forces in the fifty years since he assumed power.