Delay in possible Israel ground assault provides troops with better prep, experts say

With all eyes on the Israel-Hamas war, and Israeli Defense Forces airstrikes happening daily in Gaza, world leaders and others have been anxiously awaiting what some experts say is an inevitable ground operation into Gaza.

Since the Oct. 7 Hamas terror attack, Israeli military leaders have been mustering more than 360,000 IDF reservists from around the world and have not ruled out sending them into combat to retaliate against Hamas and rescue more than 220 Israelis who were taken hostage by the militant group.

However, Israeli officials have not formally given a timeline as to when a potential ground assault would take place. A senior U.S. official told ABC News that, as of Monday, the Biden administration has no absolute certainty when a ground incursion could begin.

Chuck Freilich, a former deputy national security adviser in Israel and long-time senior fellow at Harvard's Kennedy School, told ABC News that while he's surprised Israel has not started a ground offensive yet, he doesn't see it as a delay. Rather, he said, it's a sign Israel is doing as much it can to prepare for such an operation and have as little collateral, political and long-term damage as possible.

"This is a momentous decision for Israel, and it must absolutely get it right," Freilich said. "This time, the stakes are so high."

Freilich noted that even though the IDF's reservists represent one of the largest calls to service in Israel's history, they still need time to be ready for what he said was an unprecedented mission.

Over the last few decades, the Israeli military has leaned on the service of full-time soldiers in major offenses and conflicts and has called on reservists less and less, according to Freilich.

"There was a big debate even if the reservists were combat-ready. There were some who argued they aren't," he said.

It's estimated the IDF has 605,000 active members, 35,500 of whom are full-time soldiers -- roughly 5.87% of the military unit. An estimated 139,500 are conscripts, and the remaining 430,000 are reservists.

Amichai Magen, a visiting professor of political science and Israeli studies at Stanford University's Freeman Spogli Institute for International Studies, told ABC News that the IDF also needed more time to lay out its military strategy.

Magen said that after getting caught off guard on Oct. 7 in what he called a "colossal intelligence failure followed by a colossal operational failure," the Israeli military will be working meticulously to strike Hamas targets, rescue the hostages, and avoid any Palestinian civilian and Israeli solider casualty that it can.

"Israel was taken by surprise horribly... and doesn't want to be taken by surprise again," he said. "Israel wants to choose the methods and timing of which the next phase of the war will be determined."

Magen said the current IDF airstrikes provide an operational advantage as they take out Hamas strongholds, weapons and leaders of the militant group, and "give soldiers a pathway" for their ground assault.

However, experts warn the delays will have a rippling impact on Israel's reputation, as more and more Palestinian civilians are caught in the crossfire.

"Clearly as time goes, the legitimatization of an Israeli attack diminishes," Freilich said. "As more ugly pictures [of civilians] come out of Gaza, it hurts Israel."

The Biden administration asked Israel to delay a ground incursion into Gaza to allow time for the release of more hostages and for humanitarian aid to get to civilians in Gaza, an administration official told ABC News on Sunday. The White House refused to confirm or deny the administration's request.

Magen said the support of the U.S. and other Western powers is a factor in Israel's decision, but ultimately the military will make the judgment on what it thinks is the best course.

"There is a sense the stakes are so high that this time, with or without international sympathy, Israel has no choice," Magen said.

Freilich said Israel's leaders will have to be prepared for several political and military scenarios going forward, including how their troops would fighting Hamas once they are on Gaza soil, and how long they plan on fighting there.

Magen said Israel is also preparing for the possibility that the conflict could escalate and may need to deploy its troops to other areas, including the West Bank, to fight Hamas, Hezbollah and other terrorist groups.

"The calculus has changed," he said. "Israelis feel like they are fighting with their backs against their walls."

ABC News' Martha Raddatz and Selina Wang contributed to this report.