It's the last long weekend of the summer, time to catch up on what's been happening in the war in Syria, and try to shed some light on why more than four million Syrians have fled their country.

Here are six key things to know.

Political settlement not in sight

The odds of a political settlement in the Syrian civil war currently stand at "virtually nil," the International Crisis Group says in a new report: "Diplomacy is stymied by the warring parties' uncompromising positions, reinforced by political deadlock between their external backers."

Syrian President Bashar al-Assad's principal backers are Russia and Iran, while the United States, Britain, France, Saudi Arabia, Turkey, Jordan, Qatar, and the United Arab Emirates back the armed opposition to Assad.

On a different note, Russian President Vladimir Putin told journalists on Friday that Assad has agreed to "establishing contact with the so-called healthy opposition and bringing them into governing."

ISIS holds on under U.S.-led bombardment

Noting that refugee policy doesn't offer a solution to the Syrian civil war, Prime Minister Stephen Harper said Thursday, "We have to take a firm military stance against ISIS and that's what we're doing."

The U.S.-led coalition dropped 22,863 weapons in the first year of their war against ISIS in Syria and Iraq. Two-thirds were dropped by the U.S. air force, according to the newspaper Air Force Times. The operation is costing about $9.4 million per day.

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Children sit atop of debris after what activists said was an airstrike by forces loyal to Syria's President Bashar al-Assad at Arbin town in the Damascus countryside. (Bassam Khabieh/REUTERS)

All those strikes have killed more than 15,000 fighters, according to various sources, but "Pentagon and intelligence officials admit the Islamic State group's ability to recruit has largely offset those casualties," Air Force Times reports.

"The war is not succeeding, as far as the coalition is concerned, despite the continual and very, very heavy use of air power," security analyst Paul Rogers said.

Rogers, who's with Bradford University in the U.K., says ISIS has gained a lot of territory in Syria.

"The reality is, one year after the start of the war, Islamic State is as strong as ever in Syria and Iraq, and overall it's probably increased its territory since it took Mosul [in Iraq] last year and it is developing more and more links with groups overseas," he told CBC News.

U.S. analysts estimate ISIS has about 31,000 fighters, while the U.S. Treasury Department puts ISIS's earnings from oil revenues and taxation at $1 billion US annually.

Other jihadist groups holding on, too

While ISIS is the dominant group in eastern Syria and in areas along the Turkish border, Jabhat al-Nusra, the al-Qaeda affiliate in Syria, also dominates significant territory in the north and in the western province of Idlib.

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Civil Defence members search for survivors at an al-Nusra headquarters that was targeted by what Nusra members said was a U.S.-led air strike, in Jabal al-Zawiya, Idlib June 3. (Khalil Ashawi/Reuters)

The two groups may be fighting each other in one place while fighting together against government or non-jihadi opposition forces in another place.

According to Crisis Group, much of al-Nusra's leadership is from outside Syria, especially Jordan, while the group's foot soldiers are usually from the area where they are fighting, "many likely drawn by its material resources and effectiveness rather than its distinct agenda."

They don't necessarily buy into the al-Qaeda ideology, but they do like the higher salaries offered by al-Nusra compared with the Southern Front, a coalition of 49 non-jihadi factions fighting in southern Iraq that came together last year and now has between 20,000 and 30,000 members.

Front officials told Crisis Group that al-Nusra pays their fighters about $185 US a month, while their own fighters get just $50-$70.

There are other jihadist groups fighting in Syria, some with al-Qaeda affiliations. Al-Nusra is the strongest Islamist faction in the south.

Coalition in southern Syria progressing

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Syrian emergency personnel carry a wounded man following air strikes by Syrian government forces on a marketplace in the rebel-held area of Douma, east of the capital Damascus, on Aug. 16. (Sameer Al-Doumy /AFP/Getty Images)

The south is where the jihadi groups are at their weakest. Crisis Group says the U.S. and Jordan are particularly influential in the south, and the Southern Front's formation "signalled a modest, yet significant escalation in engagement by their state sponsors — especially the U.S. and Jordan." 

The Front has chalked up modest gains against government forces but, Crisis Group says, "opposition elements cannot build effective governance amid the death and destruction caused by aerial bombardment, particularly given the regime's tendency to target precisely those facilities necessary for capacity to emerge."

Assad regime weakening

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Syria's President Bashar al-Assad (R) meets with Iranian Foreign Minister Mohammad Javad Zarif in Damascus, Syria, on Aug. 12. (SANA/Reuters)

The Assad regime's military capacity has been steadily eroding, something Crisis Group expects will continue.  

Iran-backed militias and Hezbollah forces from Lebanon often fight alongside government troops, and they say that in areas Assad fears losing, he could increase his reliance on those outside forces or concede the areas to the opposition and resort to aerial attacks, including barrel bombs, so they remain ungovernable.

Last week, a state-run Damascus television station reported that  alongside Assad's troops, Russians had been fighting rebel forces. Their video showed Russian-speaking soldiers fighting in Syria's Latakia mountains, using one of the Russian army's latest and most advanced armoured cars.

A Free Syrian Army representative told the British newspaper The Times that "the Russians have been there a long time," and their numbers have increased in recent weeks.

On Friday, Putin admitted, "we are already giving Syria quite serious help with equipment and training soldiers, with our weapons."

Turkey steps up its involvement

Turkey seriously entered the fight against ISIS in July, but with a twist. On July 25 Turkish jets began bombing ISIS targets and Kurdish targets, a staunch ISIS foe.

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Kurdish People's Protection Units (YPG) fighters take up positions in Hasaka city, Syria July 22, as they monitor the movements of Islamic State fighters who are stationed in another neighborhood. (Rodi Said/Reuters)

Kurdish fighters had played a key role in winning battles in Syria along the border with Turkey, including in the towns of Kobani and Tal Abyad.

After the first few days of bombing, the Kurds were more often the target than ISIS.

Turkey's move appears to have been part domestic policy and part foreign policy.

Eric Edelman, a former U.S. ambassador to Turkey, says the seemingly contradictory policy has as its goal winning back majority control in parliament for President Recep Tayyip Erdogan, after losing that majority in the June elections. Voters go to the polls again on Nov. 1.

Erdogan also gave the US permission to fly anti-ISIS missions from Turkey's Incirlik air base. The U.S. government has expressed support for Turkey's attacks against Kurdish forces.

Syria's centuries-old heritage sites damaged, destroyed by war: Photos