US decision to exit Syria 

However, the most significant development in Syria in 2018 is the US abrupt decision in December to withdraw all its troops from Syria, as long demanded by the government of President al-Assad.

The US forces stepped in the Syrian war in 2014, first supporting some rebel groups before ending up backing the Kurdish militia in northern Syria in its fight against the IS.

In a recent phone call with his Turkish counterpart Recep Tayyip Erdogan, US President Donald Trump reportedly said the withdrawal of the US forces from Syria will be slow and coordinated.

The ongoing US withdrawal will apparently leave the Kurdish militants in northern Syria with only two choices, either to confront the planned Turkish military campaign or to return under the umbrella of the Syrian government.

The latter one seems to be a better bet as the Syrian army declared on Friday that it had entered Manbij, a key northern city which lies about 30km south of the Turkish border, at the invitation of the Kurdish People's Protection Units (YPG) which had withdrawn from the city.

Muhannad Haj Ali, a Syrian lawmaker, described the US presence in Syria as "an act of aggression," saying its withdrawal would help the political process in Syria.

"The withdrawal comes as part of a Russian pressure on the United States to pull out in order to accelerate the Syrian political process and find a peaceful solution to the Syrian crisis," he told Xinhua.