Northwestern Idlib province and surrounding areas are home to about 3 million people - almost half of them civilians displaced from other parts of Syria. Turkey, which backed opposition forces against Assad, fears a flood of refugees fleeing a military offensive and the destabilisation of areas it now holds in Syria.
Syrian President Bashar al-Assad has massed his army and allied forces on the front lines in the northwest, and Russian planes have joined his bombardment of rebels there, in a prelude to a widely expected assault despite objections from Turkey.
Russian Federation is Assad's top worldwide backer; its support, including aircraft, special forces and mercenaries, enabled him to reverse the course of his country's seven-year civil war, which has killed hundreds of thousands of people and displaced millions more.
"The main issue with Idlib is that it is the last terrorist stronghold and there is a need to tackle it because the longer they [terrorists - TASS] remain there, the more the situation deteriorates in Syria's neighboring countries", Safronkov noted.
"The illegal presence and interference of America in Syria which has led to the continuation of insecurity in that country, must end quickly", Rouhani said. But a regime attack on Idlib will likely move ahead despite Turkey's appeals for more time to use carrot-and-stick diplomacy with the jihadis.
With little hope of stopping the government forces, protests broke out in Idlib and the nearby western countryside of Aleppo Province, with demonstrators chanting slogans against Assad.More news: F1: Vettel sets Italy pace, Ricciardo unlucky
Furthermore, just past year, Brett McGurk - the US government's Special Presidential Envoy for the Global Coalition to Counter ISIL (Daesh, ISIS) - called Syria's Idlib province "the largest Al Qaeda safe haven since 9/11, tied directly to Ayman al-Zawahiri [current leader of Al Qaeda]". But as Sam Heller, a senior analyst on non-state armed actors at the International Crisis Group, noted, "Despite US official rhetoric, the United States still only seems to have drawn a line at the use of chemical weapons, which - it's clear - would prompt US military action".
They're determined to reclaim it from the thousands of militants they say are hiding among civilians.
The SOHR said that the strikes were the fiercest in over a month of attacks on rebel-held areas in the north.
US President Donald Trump withdrew his country from the Iran nuclear deal in May, and re-imposed the first batch of anti-Iran sanctions later in August. Now, major patrons Moscow and Iran are looking to consolidate gains as the battle in Idlib approaches.
Ankara wants to "prevent attacks on Idlib", Turkish Foreign Minister Mevlut Cavusoglu said during a press conference with German counterpart Heiko Maas. All three nations agree that the threat of radical Islamists in Syria must be eliminated, but differed as to how this should be achieved.
There are an estimated 10,000 fighters, including al Qaeda-linked militants, in the province.
For Russia and Iran retaking Idlib is crucial to complete a military victory in the rebellion against Assad. USA officials have said there is no evidence the rebels in Idlib possess chemical weapons.