Getting Israel’s hostages released from Gaza and stopping the war may have taken two years and the direct efforts of the American president and the leaders of several Arab and Muslim nations.

But that was almost certainly the easy part.

Getting Hamas to give up its weapons, and demilitarizing the Gaza Strip — key preconditions for Israel to pull out of Gaza fully, as both President Trump and Prime Minister Benjamin Netanyahu reiterated on Monday — could prove a lot harder.

Then there are the other issues in Mr. Trump’s 20-point plan, which outlined a comprehensive solution for Gaza. In full, it also called for the establishment of an international force to help maintain security in the territory, an ambitious effort to rebuild Gaza’s economy and infrastructure, and the creation of a temporary Palestinian governing committee, whose work would be overseen by an international board.

During the talks leading up to the cease-fire in Gaza, provisions for who would run the enclave on “the day after” the war was over were among the most complicated and vexing — so much so that they were eventually severed from the cease-fire talks and put off until a second phase of negotiations.

That phase had at least an air of auspiciousness on Monday evening in Sharm el-Sheikh, Egypt, where Mr. Trump and President Abdel Fattah el-Sisi of Egypt gathered dozens of leaders to try to build on the momentum created by the truce and the exchange of 20 living Israeli hostages and the bodies of others for nearly 2,000 Palestinian prisoners.

“Phase 2 has started,” Mr. Trump said. He predicted “tremendous progress.”

“It’s peace in the Middle East,” he said. “Everyone said it’s not possible to do. And it’s going to happen.”

Yet, Monday’s kickoff in Sharm el-Sheikh aside, it is unclear even when Phase 2 talks will formally begin and where they will be held.

And both Israeli and Palestinian analysts said it was easier to imagine things going sideways than to imagine Mr. Trump’s plan being fully realized.

“The main issue still hasn’t been solved: Hamas’s weapons,” said Akram Atallah, a London-based Palestinian columnist originally from Jabaliya, in the northern Gaza Strip. “The Israelis are demanding Hamas disarm, which is not a simple administrative measure. Hamas was founded on the basis of bearing arms.”

Hamas, he said, is effectively being asked to “dismantle its ideology.”

With the halt to a war that has killed tens of thousands of Palestinians and lain waste to much of Gaza, Mr. Atallah said that the current atmosphere was more optimistic but that it was uncertain how long that would last.

“It feels good right now,” he said, “but I can see dark clouds in the distance and I don’t know what they’re carrying.”

Israeli analysts and officials said the likeliest outcome was that Phase 2 of the talks would become bogged down. They envisioned the status quo lingering for so long that it takes root, with Hamas still armed, and the Israeli military refusing to withdraw fully from Gaza. In that circumstance, they also foresaw the Israeli military treating the group much as it now treats Hezbollah in Lebanon: occasionally striking Hamas militants or their weapon depots from afar.

Despite Mr. Trump’s repeated, unqualified declarations that the war is over, backsliding on either side could threaten a renewal of fighting, analysts said.

“If there’s a terrorist attack against one of our posts right now, God forbid, and we have casualties, after a minute, it’s over,” said Zohar Palti, a former senior Mossad and Ministry of Defense official.

Nimrod Novik, a former Israeli envoy and distinguished fellow at the Israel Policy Forum, warned of the influence of domestic politics. “If it turns out in four or five weeks that the general mood in the country is that this war was an awful round, but only another round, and Hamas is back, I can see Netanyahu trying to correct that,” Mr. Novik said, alluding to the possibility of a resumption of hostilities. “All you need is a Hamas provocation and a disproportionate Israeli reaction, and you can have a spiral.”

It was up to Qatar, Turkey and Egypt — the three Muslim-majority countries that played major roles in mediating the Hamas-Israel cease-fire — “to pressure Hamas not to provoke,” Mr. Novik said.

To members of Mr. Netanyahu’s governing coalition, the onus is squarely on Hamas. Several officials described the cease-fire agreement so far as amounting to a simple trade in which Israel gave away roughly half of Gaza in exchange for its hostages. To get Israel to leave the rest of Gaza’s territory, they said, it will need to give up its arms and let another entity step in to govern the enclave.

“Things are very straightforward,” said Boaz Bismuth, a Netanyahu ally who heads the Knesset’s foreign affairs and defense committee. “If you don’t want Israel to be there, you know exactly what you have to do. It’s easy.”

But saying so doesn’t make it so.

Hamas, experts close to the militant group said, is willing to make certain moves to enable the reconstruction of Gaza, but it still wants to retain some influence over the territory’s future.

“Hamas is willing to offer some concessions to enable the rehabilitation of Gaza, but it will not evaporate,” said Ibrahim al-Madhoun, a Palestinian analyst close to Hamas. “Its focus is on quiet. It wants to be part of the solution, and it won’t be an obstacle to stability.”

Mr. Palti, the former Israeli intelligence and defense official, expressed skepticism over the Trump plan’s prescription that Hamas be barred from either a military or civilian role in governing Gaza.

“Who’s going to do it?” he said. “If somebody thinks that with a magic stick you’re achieving this revolution in hours or days, forget about it. It’s not going to happen. Not because I’m pessimistic; because I’m realistic.”

The deployment of an international stabilization force, as the plan suggests, could lead the Israeli military to withdraw further. But it is still largely unknown which countries would contribute to the force, how it would be funded and trained, and when it would deploy.

And the Palestinian Authority, which previously governed Gaza and still has employees on the ground, appears to be largely excluded from Mr. Trump’s initiative, barring the completion of unspecified reforms.

All of which is not to say that Phase 2 is doomed from the outset.

Mr. Bismuth, the lawmaker from Mr. Netanyahu’s party, took great encouragement from the participation of Arab countries in the peace talks, and even more from Monday’s release of 20 Israelis held in Gaza since the Oct. 7, 2023, attacks.

“I do believe that those who have to do the specific moves expected from them will do them,” he said. “When you have such results like today, you can believe in the optimistic scenario.”

Natan Odenheimer contributed reporting from Jerusalem.