The issue returned to international headlines with a series of migrant shipwrecks, part of the 2015 Mediterranean migration crisis. The International Organization for Migration (IOM) estimates suggest that between the start of 2015 and the middle of April, 21,000 migrants had reached the Italian coast and 900 migrants had died in the Mediterranean. Critics of European policy towards illegal migration in the Mediterranean argue that the cancellation of Operation Mare Nostrum failed to deter migrants and that its replacement with Triton "created the conditions for the higher death toll".