Final answer:
The transatlantic leg of slavery began in the 15th century, with Portugal likely leading the first voyage in 1444.
Step-by-step explanation:
The transatlantic leg of slavery began in the 15th century. It is believed that Portugal led the first voyage, with the establishment of the Atlantic slave trade starting in 1444. Portuguese explorers began capturing and transporting Africans across the Atlantic to work as slaves in Europe and the Americas.
Learn more about Origins of the transatlantic slave trade