Separatist rebels and Indonesian troops are preparing to hand over weapons and withdraw thousands of troops from the forested hills of Aceh province.
The peace deal to end a 29-year civil war is seen as Aceh's best chance in years to bring a permanent end to the fighting that has claimed 15,000 lives, many of them civilians.
It will also help ease the flow of aid to victims of the December 26th tsunami.
But analysts warn that if the agreement unravels it will happen during the delicate phase of disarmament and demobilisation - a four-month operation that starts on Thursday under the watchful eye of EU and Southeast Asian peace monitors.
Free Aceh Movement rebels say they will surrender a quarter of their 840 weapons by Sunday. The military will respond by pulling out the first 6,000 of 27,000 troops, with another 25,000 remaining behind.
The peace deal was signed in Helsinki, Finland, last month, but having seen the collapse of several earlier accords, many people said they were waiting to see how things played out on the ground.
The military and the rebels have repeatedly said they would abide by the agreement - arguing that peace in Aceh would benefit all - but in the days leading up to the critical weapons handover both sides seemed uneasy.