MPs will later vote on extending UK air strikes upon Isis from Iraq into Syria.
One of prime minister David Cameron's main arguments for intervention in the complicated civil war is that there are 70,000 'moderate' rebel fighters prepared to fight Isis on the ground - but many doubts have been raised by security advisors and regional experts on the validity of this claim.
The Free Syrian Army, once a strong rebel force which came close to totally liberating Aleppo from regime forces in 2012, are now under siege from the Bashar al-Assad regime in the south of the country, and the regime, Isis and Russia air strikes in the north, as can be seen in the map below.
Most rebel groups making any gains are jihadi forces of varying stripes, including Al-Qaeda offshoot al-Nusra:
The key exceptions are the Kurdish (YPG and YPJ) armies in the north of the country, represented in the above map in purple, who drove out Assad's soldiers in the early days of the war and have managed to declare and maintain an autonomous, largely peaceful and democratic region in the midst of the Isis bloodshed that surrounds it.
Rojava, as it is known, is both feminist and polyethnic. Provisions written into its constitution ensure each municipality must elect Kurdish, Arab and Christian representatives, and one of the three must be a woman.
The statelet is also defended by the "YJA Star" feminist army, known in English as the "Union of Free Women", and is backed by PYD and YPG militia, the Syrian affiliates of the PKK, the Kurdish movement that has been fighting the state in Turkey on and off since the 1980s.
And having fought so hard for autonomy in Syria, the Kurdish forces are not about to give it up by fighting a war that doesn't interest them.
In Iraq, where there have been coalition air strikes against Isis since mid-2014, Kurdish (peshmerga) fighters have had success in retaking territory from Isis.
The YPG and YPJ in Syria will also be helped by UK strikes - but they have little interest in fighting outside of their own territory, or liberating the country as a whole.
What's more, as Rojava flourishes, the more likely it is that seeds of unrest are sown in Kurdish areas of Turkey and Iraq.
The Independent's Middle East correspondent Patrick Cockburn has described the YPG as "the most effective anti-Isis ground force" - but funding them will not only enrage Turkey, a Nato member and UK ally, it is unlikely to bring peace to Syria at large either.