The battle for Mosul is a chance for President Barack Obama to claim an election-year victory over the Islamic State group in Iraq and offset failures in Syria.

Ask the White House about the slow motion catastrophe in Syria and, more likely than not, officials will talk about the different -- if related -- problem of the Islamic State group.

A multitude of rival authorities and factions are contesting power amid the anarchy that has gripped Libya since its 2011 revolution which ousted longtime dictator Moamer Kadhafi.

Below is list of the main warring forces.

US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov meet on Saturday in Lausanne in the latest bid to ease the bloodshed in Syria.

UN peace envoy Staffan de Mistura will also attend, along with the chief diplomats from Turkey, Saudi Arabia and Qatar -- all backers of Syrian opposition forces.

State television threatens the West with nuclear weapons, the Kremlin halts a disarmament treaty, the army warns of shooting down US jets. As ties between Russia and the West have once again slumped, rhetoric in Moscow has peaked.

Whoever occupies the White House next, he or she will inherit one of the most complex and brutal crises in the world: the war in Syria.

With Syrian President Bashar Assad and his allies Russia and Iran dug in, neither Hillary Clinton nor Donald Trump has articulated a comprehensive or realistic proposal that would address the multiple strands of the conflict.

For the second US presidential debate, Sunday night in St Louis, the pressure is squarely on Donald Trump, who needs a moment of political magic to reverse his slide in polls barely four weeks from Election Day.

- Donald Trump -Even though the Republican candidate trails Hillary Clinton in the polls, he wasted opportunities to regain the advantage over his Democratic rival in their September 26 showdown. 

The Nobel Peace Prize, awarded Friday to Colombian President Juan Manuel Santos despite a popular rejection of the terms of his deal with FARC rebels, has highlighted fragile peace processes several times in the past.

Nearly a month after the September 11 attacks that killed 3,000 people, the US launched its first major salvo in the "war on terror" by invading Afghanistan -- where, 15 years on, thousands continue to die each year.

Palestinian President Mahmoud Abbas received a clean bill of health after undergoing an emergency heart procedure on Thursday. But his brief hospitalization drew attention to the lack of a clear successor to the aging leader and the ongoing rift between rival governments in the West Bank and Gaza Strip.

Abbas, leader of the Fatah Party, was elected president of the Palestinian Authority in 2005 in what was supposed to be a four-year term. One year later, the rival Hamas militant group defeated Fatah in parliamentary elections and violently seized control of Gaza in 2007. Abbas has remained in control of parts of the West Bank ever since, while no national elections have been held.

With Barack Obama's presidency coming to a close and US policy for Syria at an impasse, Vladimir Putin's Russia has stepped up efforts to secure its ally Bashar al-Assad in power.

US officials fear the Kremlin is racing to consolidate its gains in Syria before a new, possibly tougher administration takes charge, but there is little sign of a clear new policy emerging.