It was the demand that broke the ceasefire, but also the demand that in the end helped make the peace. When that 15-letter word - decommissioning - was first introduced into the peace process, we didn't really know what it meant or what to make of it.
The different interpretations could not have been further apart, stretching from confidence building to surrender.
But rather than bend to the demands of the then Major Government, the IRA bombed London, and the ceasefire crumbled in the Canary Wharf bomb of 1996 - two lives lost in the rubble.
And just weeks after the IRA drove two bombs into Thiepval Barracks, the Army's Northern Ireland Headquarters, one of the republican wordsmiths of that period Jim Gibney answered the decommissioning question, describing it as "fatal to the peace process".
In those five, short words you get some idea of the mind barriers that had to be cleared; decommissioning was going to be a long run, not a quick fix.
Many of us will remember the different phrases and responses that grew out of that word decommissioning, 'not a bullet, not an ounce' and 'no guns, no government' probably the two that are best-known. Loyalists, including the veteran leader Gusty Spence and Michael Stone, suggested the weapons should be allowed to rust into disuse.
In the developing peace process, it was one of the hardest nuts to crack, but it eventually happened.
It was done secretly and inside a process managed by the Independent International Commission on Decommissioning (IICD).
Its patient work stretched from August 1997 to February 2010. General John de Chastelain has been part of the process for all of that period.
The process started with one of the loyalist splinter groups - the LVF. In December 1998, bits and pieces of guns and pipe-bombs and bullets were brought to a workshop in east Belfast to be destroyed.
I was one of a small number of journalists who watched it happen. It wasn't much of a start, but it was beginning.
Throughout the long process, though, the main focus has always been on the IRA. And there would be no journalists present when that organisation came to decommission.
Two churchmen were present as witnesses - one of them former Methodist President Harold Good.
"What I've often said is what I saw was hugely significant, but what I heard was no less so," he said. "Putting together what I saw and what I heard, I was left in no doubt that their war was now over.
"The day after our announcement, David Ervine came to see me and he asked me did I feel privileged to be there. On reflection, there's no greater privilege than to be trusted, and in that sense I was privileged. That trust is something that I will never betray."
David Ervine died before the main loyalist organisations including the UVF moved to put their arms beyond use. That was last summer and then the UDA followed.
In the big freeze of winter, that organisation delivered its ammunition to the de Chastelain team wrapped in socks, and at the Ballykinler Army base those bullets, along with guns and rows of pipe bombs were destroyed.
According to one of the group's leaders, Jackie McDonald, that act was about delivering a big message.
"The fact that all the bona fide organisations if you like gave up the guns, they are sending out a message to the dissidents that violence doesn't work."
But those dissident groups are still trying to make it work: in the bomb at Newry courthouse; in the device under Peadar Heffron's car; in the shooting attacks last year at Massereene Barracks, and then in Craigavon. But McDonald is right - the long wars are over.
Decommissioning did not remove every weapon, bullet and ounce of explosive, but the process sent out that big message - that those who fought the wars were ending them.
It took time and it took patience and its significance was probably captured in another quote from Jim Gibney.
"They [the IRA leadership] turned history on its head and, in doing so, they turned the IRA upside down as well."
The message - 'not a bullet, not an ounce' - had to change. It was all part of making the peace.