The war in Syria, now in its ninth year, has witnessed yet another escalation as the Syrian government and its allies have launched a campaign against the opposition-held areas in the country's northwest.

In recent years, as Syrian government and allied forces took over opposition-held territory across the country, hundreds of thousands of civilians and opposition fighters from those areas were bussed to Idlib province.

Parts of Idlib and Aleppo provinces are now the front lines of the battle between Syrian armed opposition groups, some of whom are supported by Turkey, and Russia and Iran-backed forces loyal to Syrian President Bashar al-Assad, who is pushing to regain control of the whole country.

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The government has sought to take control over the strategic M5 highway, which runs through Aleppo and Idlib provinces and which was once a major commercial route linking Aleppo to Damascus and the south of the country.

Idlib is also adjacent to Latakia province, a Syrian government stronghold that is home to the Russian military airbase Hmeimim.

In 2018, the advance of government forces on Idlib was paused when Turkey and Russia agreed to create a demilitarised zone in the province from which some opposition groups would withdraw.

But in April 2019, the government launched a military offensive backed by Russian air power on opposition positions in the region. While a number of ceasefires were agreed to in the summer, they quickly collapsed and in December forces loyal to Damascus launched a new aerial and ground campaign.

The conflict escalated further earlier this month when several Turkish military personnel were killed by Syrian government forces, prompting a military response from Ankara.

Idlib province is currently home to more than three million people, the majority of whom are internally displaced. According to the United Nations, the latest push has forced more than 700,000 people from their homes, most of whom have fled to camps along the sealed border with Turkey.

Aid workers have warned that the humanitarian situation at the overcrowded border area has become dire. There are about one million Syrian refugees living near the border, with IDP camps already at full capacity. The UN has warned of an impending "humanitarian catastrophe".