The Land Forces practice extensive year-round military training in various conditions. Cooperative drills with the United States are very common, the last series of them conducted in 2008. Bulgaria's most recent full-scale exercise simulating a foreign invasion was carried out in 2009. It was conducted at the Koren range, and included some 1,700 personnel with tanks, ATGMs, attack aircraft, AA guns and armored vehicles. The combat skills of individual soldiers are on a very high level, on par with troops of the U.S. Army.