The Utility of Force: The Art of War in the Modern World is a treatise on modern warfare written by General Sir Rupert Smith and published in 2005. Smith is a retired general who spent 40 years in the British Army; he commanded the 1st Armoured Division in the First Gulf War and served as General Officer Commanding Northern Ireland at the end of the Troubles. He was motivated to write the book by his experiences in the Balkans. He commanded the United Nations Protection Force (UNPROFOR) in Bosnia from 1995 to 1996, during which time the Srebrenica massacre occurred and the capital, Sarajevo, was under siege by Serb forces. Smith was instrumental in the lifting of the siege by arranging for NATO air strikes and an artillery barrage. This enabled a ground assault by Bosnian and Croatian forces that ended the siege and led to the Dayton Agreement. Smith's second involvement with the Balkans was in 1999 during the Kosovo War, when he was serving as NATO's Deputy Supreme Allied Commander Europe, overseeing air strikes against Serb targets.