Here is a breakdown of the main forces fighting Islamic State jihadists in Iraq and Syria, after British lawmakers on Wednesday voted to join the U.S.-led bombing campaign in Syria:

- Syrian and Iraqi armies -- SYRIA: The Syrian army numbered 178,000 troops in 2015, according to the International Institute for Strategic Studies (IISS). Syria's army has been roughly halved from its pre-war strength by deaths, defections and increased draft dodging. In its fight against rebels and jihadists, it relies on militias, which claim 150,000 to 200,000 members.

Riding on horseback and motorbikes, commander Naeem's fighters combed a fog-enveloped Taliban infiltration route in Afghanistan's northern badlands, as the government expands anti-insurgent militias across a patchwork of fiefdoms.

Desperate to muzzle the resurgent Taliban, the government is cultivating thousands of militias with chequered pasts as a short-term security fix to supplement ground troops suffering record casualties.

The U.S.-led coalition has made Iraqi and Syrian Kurdish forces primary allies against the Islamic State jihadist group, but over-reliance on the Kurds carries risks, analysts warn.

As the world seeks to turn up the heat on IS, some of the West's main partners on the ground are the peshmerga forces from Iraq's autonomous Kurdish region and the Kurdish People's Protection Units (YPG) in Syria.

Global oil producers, who provide the world with much of the fossil fuel that causes global warming, are in no hurry to brighten up their own image as climate dinosaurs.

Some Gulf countries have timidly started investing in renewable energy, but experts say the initiatives are just a tiny crack in producers' otherwise solid front of indifference to climate change.

Turkey's downing of a Russian jet has played into the hands of Syrian President Bashar Assad by bringing Moscow on board with his bitter opposition to Ankara, experts say.

On Thursday, Moscow announced it was preparing economic measures against Ankara two days after Turkish forces shot down a Russian plane that crashed in Syrian territory.

Turkey's downing of a Russian war plane on the Syrian border risks inflicting significant damage on relations between Moscow and Ankara, even if they both have an interest in avoiding a permanent rupture.

Modern Turkey and Russia are the successor states of empires that fought over three centuries of war from the late 16th century for the Black Sea and Caucasus but in recent years forged a sometimes uneasy but pragmatic alliance.

Despite talk of a grand coalition between Russia and the West against the Islamic State group, experts warn that any such project would quickly run into obstacles.

Russia's ambassador to France became the latest diplomat to push the idea of greater cooperation between East and West on Wednesday, floating the prospect of a "joint command" against Islamic State (IS) jihadists.

Despite talk of a grand coalition between Russia and the West against the Islamic State group, experts warn that any such project would quickly run into obstacles.

Russia's ambassador to France became the latest diplomat to push the idea of greater cooperation between East and West on Wednesday, floating the prospect of a "joint command" against Islamic State (IS) jihadists.

Belgium is battling accusations that it has become a "failed state" whose linguistic and communal divisions contributed to failures that let it become a jihadist base for the Paris attacks.

Years of increasing federalism have deepened rifts between the wealthy country's French-, Flemish- and German-speaking regions, leaving it with little sense of nationhood and a dysfunctional, multi-layered bureaucracy.

Turkey's downing of a Russian war plane on the Syrian border risks inflicting significant damage on relations between Moscow and Ankara, even if they both have an interest in avoiding a permanent rupture.

Modern Turkey and Russia are the successor states of empires that fought over three centuries of war from the late 16th century for the Black Sea and Caucasus but in recent years forged a sometimes uneasy but pragmatic alliance.