PARIS — In France’s first airstrikes against Islamic State militants in Syria, warplanes destroyed a training camp, President François Hollande announced on Sunday. At a news conference in New York, where he had arrived for the United Nations General Assembly, Mr. Hollande said that the warplanes had attacked the training camp in eastern Syria after it had been identified by French air surveillance with help from the coalition of Western and Middle Eastern states conducting the air campaign against the Islamic State, also known as ISIS, ISIL or Daesh. “Our forces reached their objectives: The camp was completely destroyed,” Mr....