How did Israel and the U.S. miss what Hamas was planning?

The surprise attack by Hamas on Israel suggests a massive intelligence failure as the Israeli government appeared blindsided by the infiltration of Hamas fighters across the southern border and the launch of thousands of rockets.

The Hamas assault by air, land and sea also raised questions as to why U.S. intelligence agencies apparently did not see it coming, experts and former intelligence officials said.

U.S. officials said that if the Israelis knew an attack was imminent, they did not share it with Washington.

“We were not tracking this,” one senior U.S. military official told NBC News.