Australia has joined this latest coalition of the willing, and pressure will go on New Zealand to do likewise.
United States President Barak Obama was hesitant as the Islamic State persecuted and killed Iraqis and Syrians be they other Muslims (the majority), Christians or Yazidis.
The beheading of two United States journalists (since then a British aid worker has also been killed) laid bare a menace many saw as too big to ignore.
A evil fundamentalist radical Islam group flourished and expanded and needed to be stopped.
But is that possible? And how?
Western intervention in Vietnam, Afghanistan and in Iraq has all ended in tears.
What often begins as a small commitment of ''advisers'' expands.
''Mission creep'' takes place again and again.
In this case, President Obama's strategy in essence is to increase air strikes, provide training and intelligence for groups already battling the Islamic State (IS), send service personnel in support but not as combat troops, continue humanitarian help and to try to stop the financing of IS and the flow of foreign fighters.
Air strikes could also extend into Syria.
Australian Prime Minister Tony Abbott, who calls IS a ''death cult'', is sending special force soldiers among 600 personnel as well as air support.
He describes the mission as essentially ''a humanitarian operation'', although he concedes special forces could act as military advisers.
How easily, as Mr Abbott seems to acknowledge, this slips into actual combat.
Could the West just stand back and watch that farce of an Iraqi army be beaten up?
Even after American air strikes, could any Middle Eastern forces actually do the job on the ground?
Air superiority, too, might be militarily effective on open ground but would be much less effective in any battle for cities.
New Zealand is entangled with the United States, Canada, Australia and Britain through the five eyes intelligence network as well as in other ways.
The pressure will go on this country, too, to contribute.
With a looming election, New Zealand has the best possible excuse to prevaricate, and it was able to minimise any earlier close involvement in Iraq.
There will soon come a time, however, when some sort of commitment is required.
While caution is required, the threat of IS both locally and beyond demands a response.
The world cannot stand aside and let murderous IS expand.
The situation is different from the earlier invasion of Iraq or engagements in Vietnam or Afghanistan.
Nevertheless, the approach to restricting and undermining IS must be realistic, nuanced and across several fronts.
The image of Western infidels throwing their weight and military technology around will simply play into the hands and the minds of many Muslims - even when invited by the current Iraqi president.
What begins as popular action in both the home and host nations turns sour quickly.
The ethnic, tribal and religious stew makes any involvement a nightmare. Spice the situation with corruption, few jobs, young populations and unstable government and finding solutions becomes no easier.
President Obama talks of ''destroying'' IS.
Is that really possible when IS already has state-like apparatus in place and already controls a large swath of territory?
Therein also lies the problem of what would take its place.
Libya is a disconcerting example of an unstable and fragmented aftermath.
The United States and other parts of the world are being drawn into active resistance to the threat of IS.
In many ways, IS will be keen for this because of the opportunities that provides to alienate many more Muslims.
That was an outcome from the overreaction to 9/11.
Knowing that, the United States and others must be prepared for what could be a long and complex undertaking.
It is going to require great skill, diplomacy and wisdom to join together with various Middle East interests to contain and weaken IS.
Hopefully, this time, the worst of the quicksand can be avoided.
