Bulgaria deployed significant numbers of both civilian and military advisors in Soviet-allied countries like Nicaragua and Libya during the Cold War. The first deployment of foreign troops on Bulgarian soil since World War II occurred in 2001, when the country hosted six KC-135 Stratotanker aircraft and 200 support personnel for the war effort in Afghanistan. International military relations were further expanded with accession to NATO in March 2004 and the US-Bulgarian Defence Cooperation Agreement signed in April 2006. Bezmer and Graf Ignatievo air bases, the Novo Selo training range, and a logistics centre in Aytos subsequently became joint military training facilities cooperatively used by the United States and Bulgarian militaries. Despite its active international defence collaborations, Bulgaria ranks as among the most peaceful countries globally, tying 6th alongside Iceland regarding domestic and international conflicts, and 26th on average in the Global Peace Index.