Final answer:
Portugal began capturing African slaves in 1442, marking the start of the transatlantic slave trade.
Step-by-step explanation:
The country that began to capture African slaves in 1442 was Portugal. Portuguese explorers set out along the west coast of Africa seeking gold, spices, and new trade routes.
The first slaves were brought back to Portugal in 1441, and by 1444 the slave trade was well established, with 235 African slaves arriving in Lagos, Portugal. This marked the beginning of a vast and tragic transatlantic slave trade which grew significantly with the European colonies' demands in the New World.