(DailyMail) -- Though officials warn that military action will continue for some time, they are generally upbeat about the progress and quickening momentum of the fight.
After months of brutal, street-by-street combat, ISIS has now lost control of most of its stronghold of Mosul in Iraq, while the terrorists have become largely isolated in their Syrian bastion of Raqa.
Pentagon chief Jim Mattis and his Danish counterpart Claus Hjort Frederiksen are among the senior leaders from 15 countries attending Tuesday's summit.
"We're going to look to the future, determine what more is needed, if anything," Mattis told reporters ahead of his arrival in Denmark.
Several coalition countries are keeping a nervous eye on the region as ISIS-held territory diminishes.
Thousands of foreign fighters remain in Iraq and Syria, and coalition nations -- particularly in Europe -- are bracing for a possible wave of battle-hardened terrorists returning home.
According to a senior US administration official, Interpol has identified 14,000 foreign fighters it knows has travelled to Syria and are still alive.
The largest numbers come from Tunisia, followed by Saudi Arabia.
Thousands more have travelled from Europe, including 100 or so from Denmark, said the official, who asked not to be named.
The international law enforcement agency Interpol is now part of the anti-ISIS coalition, becoming the alliance's 68th member.
- Bombs in cupboards -
The campaign against ISIS began in autumn 2014.
Iraq's second city Mosul is now mainly back under Iraqi control, though ISIS continues to hold the Old City on the west side, where its fighters are preparing for a bloody last stand.