JERUSALEM —An Israeli soldier was sentenced Tuesday to 18 months in prison for killing a badly wounded Palestinian assailant as he lay on the ground, in a landmark decision that deepened fissures in Israeli society and drew Palestinian criticism for being too lenient.

Leading nationalist Israeli politicians called any jail time unfair and urged an immediate pardon, while Palestinians dismissed Israel’s justice system as a “joke.”

The sentencing of Sgt. Elor Azaria culminated a saga that has bitterly divided the country. While Israel’s top generals pushed for the prosecution of a soldier they say violated the military’s code of ethics, large segments of the public, including politicians on Israel’s nationalist right, sided with Azaria. Prime Minister Benjamin Netanyahu gave lukewarm support to his military.

Although the sentence was lighter than expected, those divisions showed no signs of easing following Tuesday’s sentencing in Tel Aviv.