ISTANBUL — Turkey’s fourth military operation in Syria in as many years has divided the country along the same political fault lines that have polarized it in recent years, with the government’s supporters seeing an urgent threat emerging south of the border and its critics fearing Turkey is sliding deeper into the Syrian quagmire.

Fighting in Syria’s northwest province of Idlib, the last stretch of territory held by Turkish-backed opponents of Syrian President Bashar al-Assad, has intensified dramatically as Turkey downs Syrian jets and bombs air defense systems in Operation Spring Shield, launched at the weekend. At least 34 Turkish soldiers were killed Feb. 27 in Idlib in an airstrike blamed on Syria.

Turkey wants to halt the Syrian army’s advance, which has already forced almost 1 million people to flee to its closed border. The military campaign is accompanied by another effort to placate public anger over the large number of refugees already in Turkey. The government late last week ordered border guards manning its western frontiers to stand down and invited millions of migrants to leave for Greece. 

The deaths of the soldiers shocked Turkey, marking the most fatalities its army suffered in a single attack since the early 1990s. Taxis formed a huge procession in central Istanbul early on Tuesday, waved flags and blasted their horns to honor the soldiers. Spontaneous marches took place in several cities. Members of Turkey’s tiny Jewish community prayed for the dead on Shabbat in Hebrew and Turkish.