Slave trade
In 1562, the West African slave trade was a duopoly dominated by the Portuguese and the Spanish. Sir John Hawkins devised a plan to break into that trade, and enlisted the aid of colleagues and family to finance his first slave voyage. Drake was not part of that group of financiers, though his presence as one of hundreds of seamen on Hawkins's first two slaving voyages has been assumed. There is some anecdotal evidence to support Drake serving as a common seaman on the first two voyages, and good evidence of his presence for the last two of four slaving voyages made by Hawkins' ships between 1562 and 1569.
In 1562, Hawkins sailed to the coast of the Sierra Leone, seized Portuguese slave ships, and sold the Africans in the Spanish Indies. It was highly profitable, so for his second slave voyage in 1564, Hawkins gained Queen Elizabeth I's support. She lent him one of her ships, Jesus of Lübeck, which served as his flagship. Hawkins attacked an African native town and sold many of its inhabitants in Spanish ports on the Caribbean mainland, making another large profit for himself, the Queen and the consortium of investors from her court. Sources vary on the dates and the age of Drake at the time; Harry Kelsey says he was twenty years old, "[a]ccording to Howes" (in reference to the English chronicler Edmund Howes writing in 1615). Drake was not a member of that consortium, but the crew would have received a small share of the profits. Based on this association, scholar Kris Lane lists Drake as one of the first English slave traders.
The Spanish and Portuguese were aggrieved that the English had entered into the slave trade and were selling slaves to their colonies despite being forbidden from doing so. Queen Elizabeth I, under pressure to avoid an armed conflict, forbade Hawkins from going to sea for a third slave voyage. In response, he set up a slave voyage with a relative, John Lovell, in command in 1566. Drake accompanied Lovell on this voyage. The voyage was unsuccessful, as more than 90 enslaved Africans were released without payment.
In 1567, Drake accompanied Hawkins on their next and last joint voyage. The crew attempted to capture slaves around Cape Verde, but failed. Hawkins allied himself with two local kings in Sierra Leone who asked for help against their enemies in exchange for half of any captives they took. Attacking from both sides, they took several hundred prisoners, though Kelsey says the kings kept "the larger share of slaves and dared Hawkins to do anything about it".
Events worsened for the fleet as it faced storms, Spanish hostility, armed conflict, and finally a hurricane that separated one ship from the rest, and it had to find its own way home. The remaining ships were forced into the port of San Juan de Ulúa near Vera Cruz so they could make repairs. Soon afterward the newly appointed viceroy of New Spain, Martín Enríquez de Almanza, arrived with a fleet of ships. While still negotiating to resupply and repair, Hawkins' ships were attacked by the Spanish ships in what became known as the Battle of San Juan de Ulúa. The battle ended in an English defeat with all but two of the English ships lost. The Spanish launched a fireship against Hawkins' flagship Jesus of Lübeck, and the crew of Minion in panic and fear cut the lines securing them to Jesus. Hawkins was among those who jumped from the flagship's bulwarks to Minion's decks. Drake, by this time the captain of Judith, fled leaving Hawkins behind. Hawkins escaped on Minion and limped back to England with dozens of his men dying along the way, and arriving with a crew of just 15. Hundreds of English seamen were abandoned.
After arriving back in England, Hawkins accused Drake of desertion and of stealing the treasure they had accumulated. Drake denied both accusations, asserting he had distributed all profits among the crew and that he had believed Hawkins was lost when he left. The bitter end of the fourth voyage turned Drake's life in a different direction: thereafter he would not pursue trading and slaving but would, instead, dedicate himself to attacking Spanish possessions wherever he found them. Drake's hostility towards the Spanish is said to have started with the battle and its aftermath.
The voyage of 1567–1569 was Drake's last association with slaving. In total, approximately 1,200 Africans were enslaved on these four voyages, and an estimated three times as many Africans were killed (based on the contemporaneous accounts of slavers). On the issue of slaving, scholar John Sugden writes that "Drake was in his twenties and did not question what his elders accepted", but must share some culpability for his participation.