WASHINGTON --  The United States sent a team of senior officers to Israel three months ago to learn from Israel's tactics in Operation Protective Edge in Gaza over the summer, Chairman of the Joint Chiefs of Staff Martin Dempsey said on Thursday.

Dempsey praised the IDF for taking "extraordinary lengths to limit collateral damage and civilian casualties" in its war against Hamas. The militant organization, Dempsey said, "had become very nearly a subterranean society," burrowing underground and hiding amongst the civilian population.

"We sent a team of senior officers and non-commissioned officers over to work with the IDF to get the lessons from that particular operation in Gaza," he told an audience at the Carnegie Endowment. He referred to the group of officers as the "lessons learned team."

Dempsey noted Israel's development of new techniques, such as "roof knocking," warning residents of an incoming strike.

"They would display leaflets to warn citizens and population to move away from where these tunnels," the general said. "But look– in this kind of conflict, where you are held to a standard that your enemy is not held to, you're going to be criticized for civilian casualties."

Roughly 2,100 Gazans were killed in 50 days of fighting, in which Israel was targeting tunnel infrastructure and rocket launchers built and operated by Hamas.

Determining just how many of those killed were civilians and how many were operatives is difficult to independently verify.

Both Hamas and Palestinian Authority leaders, including President Mahmoud Abbas and United Nations envoy Riyad Mansour, accused Israel of committing genocide in the campaign. The PA has threatened in recent weeks to join the International Criminal Court and press Israel on allegations of war crimes and crimes against humanity.

Hamas is listed as a terrorist organization by the United States, European Union and Israel.