(NewsNation) — Two days after Hamas launched an incursion against Israel, questions remain about how the Israeli intelligence service and military was caught off guard by the attack.

Michael Oren, the former Israeli ambassador to the United States, says “groupthink” about Hamas may have contributed. He said the perception was that Hamas wore two hats — one as being a terrorist organization and the other a governing agency for Gaza.

“There was a feeling in Israel that Hamas was increasingly focused on the sovereign (governing) hat, and that if you dumped a lot of Qatari cash in the lap of Hamas, if you let 20,000 Gazans come into Israel to work every day, that would give Hamas something to lose if it started firing at us and would certainly make Hamas focus more on its civic sovereign responsibilities. It turns out, it’s completely wrong,” Oren said Monday during “The Hill on NewsNation.”

Instead, Hamas launched the biggest attack on Israel in years. Thousands of rockets were fired into Israel and militants stormed through villages, killing and kidnapping civilians.

On Monday, the Israeli military said it had largely gained control in the south after the attack caught its vaunted military and intelligence apparatus completely off guard and led to fierce battles in its streets for the first time in decades. Hamas and other militants in Gaza say they are holding more than 130 soldiers and civilians snatched from inside Israel.

Around 900 people, including 73 soldiers, already have been killed in Israel, according to media. In Gaza, more than 680 people have been killed, according to authorities there; Israel says hundreds of Hamas fighters are among them. Thousands have been wounded on both sides.

“These people are so subhuman that they don’t care about their own people,” Oren said of Hamas. “They’re going to use them as human shields, and now going to use our hostages as human shields.”

The Associated Press contributed to this report.