They're a far cry from the typical 'Dogs of War' image many people have of mercenaries.

There is good reason for that. Put simply, they are not mercenaries.

I'm speaking of the foreign volunteers who are increasingly joining the ranks of Kurdish fighters battling the jihadists of the Islamic State (IS) group in Syria and Iraq.

As someone who was reared on the stories and exploits of those volunteers who fought with the International Brigade against fascism in Spain in the 1930's, the current crop of those taking on IS intrigues me.

By and large, it's right to be wary when weighing up or assessing the motives of such individuals. Men and women who risk all to fight in other countries wars' have always done so for a myriad of reasons.

Some indeed are driven by pure mercenarism, in it for the money and any spoils that come their way. Others do it for political or religious motives a sense of helping the underdog in a just fight. Then of course you have the outright adventurers for whom war in far off lands is an escape from a mundane existence at home.

Over the decades from Bosnia to Africa, I have encountered all of these types. Among them at their worst were a smattering of crackpots and sadists who by any definition were psychotic or dysfunctional. But along the way I met those too who truly believed they were doing good helping oppressed communities or peoples.

Those foreign volunteers in Syria and Iraq right now battling alongside the Kurdish People's Protection Unit (YPG) or Peshmerga fighters are themselves an eclectic bunch. In many ways much more so than the disenchanted Muslim boys and girls who have flocked from all over the world to the Middle East.

Within these Kurdish volunteer ranks are former soldiers, committed Christians and adventurers but the evidence is yet to be presented that any do it for money.

If they are united in one thing, it is their rejection of the brutality and oppression meted out by IS cadres.

Like all reasonable and compassionate people they recognise the importance of Edmund Burke's age old maxim that "The only thing necessary for the triumph of evil is for good men to do nothing".

The Islamic State is not al-Qaeda. It is less a covert terrorist organisation after which one goes hunting in the shadows than an army that can and should be confronted and defeated on the battlefield.

The Kurds, Yazidis and other peoples in Syria and Iraq know this, their own very existence depends on it.

They know too that if the barbarism and oppression IS readily embraces are not confronted right now in the open how can we ever possibly hope to contain its covert existence.

Time and again since the 1930's the spirit of Spain's International Brigade volunteers has been invoked whenever a fight ensues and people struggle against an evil force or regime.

I for one was wary when first I heard it used yet again in the context of the battle against IS.

Now I'm of a different view and see those volunteers fighting alongside the Kurds as worthy heirs to their historical forebears in Spain.