Sunday's delayed start to the Gaza ceasefire and incidents on Monday in which Israeli troops shot at Palestinians approaching them underline some of the hiccups likely to face a deal that will play out in the shadow of mutual mistrust and bitterness.
Qatar and Egypt, which brokered the deal alongside the US, have set up a communications hub to tackle any problems, where officials who worked on the deal for months hope to head off new clashes between foes locked in a years-long cycle of Gaza wars.
"These kinds of deals are never easy to maintain," said Majed Al-Ansari, spokesperson for Qatar's foreign ministry.
Particularly in a war zone the situation can shift very quickly, either by accident or through political posturing on one side or another, he said.
"Any party could consider a threat a reason to violate the parameters of the agreement, and therefore we would end up with having to go in and to find a way to resume the ceasefire."
With just over an hour to go before the ceasefire was due to take effect on Sunday, Prime Minister Benjamin Netanyahu announced that Israel would not observe the halt to fighting until Hamas handed over the names of the three hostages to be released later in the day.
Fighting continued almost three hours past the deadline, while a Hamas official in the coordination room set up in Cairo discussed the delay, which Hamas put down to unspecified "technical issues" with officials.
The issue was eventually dealt with and the three hostages were released on schedule in the afternoon in exchange for 90 Palestinian prisoners freed from Israeli jails late that night, setting off emotional scenes as they returned to their families.
"We don't expect things to go according to plan," said one official briefed on the negotiations, adding that issues of this kind were not expected to derail a process that diplomats and officials have been working on for months.
"It's hard to believe that after all the work the mediators have put in and the assurances they received, both from the US and the mediators, that this deal would derail on day one," the official said.
The multi-phase deal will see an initial six-week ceasefire, during which 33 hostages will be gradually exchanged for hundreds of Palestinian prisoners, people displaced from northern Gaza will be allowed to return to their homes and Israeli troops will pull back from some positions.
During the first phase, negotiations will begin for the release of the remaining 64 hostages, consisting of men of military age and for the full withdrawal of Israeli troops. But few expect the process to go without problems.
OBSTACLES AHEAD
With an extremely low level of trust between both sides who have fought each other for generations, potential pitfalls run from accidental or deliberate confrontations during the period of withdrawal to disputes over the identity and state of hostages to be released or returned.
So far, Hamas has not said how many of the hostages are still alive. A list of the remaining 30 hostages due for release in the first phase and whether they are alive or dead is expected to be handed over on Saturday.
The Israeli military says it is seeking to avoid situations in which Gaza residents come too close to Israeli troops that are pulling back. Already on Monday, troops fired on at least eight Palestinians who approached them, medics in Gaza said.
To prevent this, it will publish maps and guidelines as the agreement progresses, making clear which areas should not be approached as the withdrawal proceeds, an Israeli military official said.
"The areas will change as the troops gradually withdraw from the Gaza Strip," the military official said.
In Israel, the deal is viewed with deep suspicion by some, who say it leaves Hamas in control of Gaza and others who worry that it effectively abandons the hostages not included in the first phase.
Already, hardliner Itamar Ben-Gvir resigned as National security Minister on the morning of the ceasefire and pulled his party from Netanyahu's coalition and others may follow.
Israeli public radio reported that Israeli officials were shocked to see the three hostages released in the center of Gaza on Sunday getting out of a car in the middle of a large crowd of people held back by Hamas fighters in uniform, and will inform the mediators that they regard such scenes as unacceptable.
But mediators are counting on positive momentum as the release of hostages and prisoners continues over the coming weeks to ease opposition.
"The pictures we have seen yesterday of the three Israeli hostages meeting with their families, embraced by their families. These are the pictures that would change public opinion in Israeli politics," Ansari said. "The same goes also for the Palestinian populace, when they see 90 of their women and children coming back to their families."
"These are the kind of pictures that change public opinion. They apply real pressure on the leadership to maintain the deal."
