What Israel's 'Significant Expansion' in Gaza Could Mean

— -- Israeli Prime Minister Benjamin Netanyahu warned that one of his options in his Gaza ground offensive is a "significant expansion," but experts said today there are a few likely moves.

Netanyahu sent thousands of troops, accompanied by tanks, into Gaza Thursday night and the offensive showed no signs of easing today.

Israel Defense Forces first announced that they would target lengthy tunnels that members of Hamas use to reach rocket launching sites and to infiltrate Israel. Hamas' rocket launchers have also been targeted. The IDF said they have taken control of 10 tunnels so far.

"Hamas' underground tunnels are made for kidnapping and murdering Israelis. That's why we are destroying them," the IDF spokesman said on their official Twitter account.

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Israel said today that their troops have moved 3 kilometers into Gaza.

"An expansion of that would involve pushing forces deeper into Gaza, but probably not entering into the major civilian areas and population centers," Jeffrey White, a defense fellow at The Washington Institute, told ABC News.

The IDF has been bolstering their forces, calling up more than 53,000 reservists over the past week.

Bruce Hoffman, the director of Georgetown University's Center for Security Studies, said the IDF is likely focused on specific targets that will serve as a stopgap to halt the rocket attacks that Israel has faced recently.

"They're going to engage in what they call 'mowing the grass,' meaning they want to make sure that after two weeks of rocket barrages, Hamas' ability to fire missiles into Israel is negated - not just in the immediate future, but for an extended period of time," Hoffman told ABC. "Israel is under no illusion that they are solving the problem, but they're just trying to buy time."

White, who specializes in Middle Eastern studies after retiring from the U.S. Defense Intelligence Service, said that if the operation is escalated, there are two likely paths that it would follow. The first would be an order to send more troops into Gaza and effectively divide the strip in two by marching down the center and cutting off Hamas’ movement throughout the territory. The second and more extreme option would be a full-scale offensive, effectively leading to a re-occupation of the area. Israel occupied Gaza from 1967 to 2005.

Many, including White, do not see a re-occupation of Gaza as a likely option because of the manpower that would require and the international outcry it would trigger.

“The Israeli government understands the downsides internationally,” said Robert Danin, a senior fellow at the Council on Foreign Relations.

He said that a massive offensive “shifts attention from the rocket attacks that led to the ground operation and onto their [Israeli] continued presence in Gaza.”

"No army in the world likes to control civilian population for an extended period of time. The Israelis don’t want to escalate. That’s what so frustrating to them. They wanted to press Hamas hard enough that Hamas would say 'Okay, uncle,'"