Drescher (2009) provides a model for the history of the abolition of slavery, emphasizing its origins in Western Europe. Around the year 1500, slavery had virtually died out in Western Europe, but was a normal phenomenon practically everywhere else. The imperial powers – the British, French, Spanish, Portuguese, Dutch, and Belgian empires, and a few others – built worldwide empires based primarily on plantation agriculture using slaves imported from Africa. However, the powers took care to minimize the presence of slavery in their homelands. In 1807 Britain and soon after, the United States also, both criminalized the international slave trade. The Royal Navy was increasingly effective in intercepting slave ships, freeing the captives and taking the crew for trial in courts.