Iran is witnessing its largest anti-government protests in decades, spreading across Tehran and other cities. In Tehran, security forces showed unusual restraint on Thursday night, avoiding direct clashes in crowded areas. This calm, however, was selective. Smaller cities and provinces saw a much harsher and deadly response. Human rights groups report over 40 deaths since protests began about two weeks ago. BBC Persian confirmed at least 21 victims, mainly from Kurdish areas and Lorestan province. Video shows security forces firing on protesters. At least four security members were also killed. Supreme Leader Ayatollah Khamenei condemned the protests as foreign sabotage. In a Friday speech, he accused demonstrators of destroying their own property "just to please the president of the United States." He warned the Islamic Republic "will not back down in the face of vandals." Iran's leadership fears US moves after recent events, including US attacks on Iranian nuclear sites last June and the capture of Venezuela's President Maduro. They worry Washington might strike Iran again. US President Donald Trump has repeatedly warned Tehran. He said the US would respond strongly if peaceful protesters are killed again. Trump claimed some deaths were due to "stampedes" but stressed Iran was told hard red lines were set. In Tehran, security forces seem cautious to avoid large bloodshed and bad images. Gunshots were heard Thursday night, but internet blackouts make verification difficult. Outside Tehran, crackdowns are swift and deadly. Iran's 2022 protests after Mahsa Amini's death killed over 500 people. The Islamic Revolutionary Guard Corps (IRGC) and Basij militia played major roles in violent suppression. The regime uses layered security forces, escalating from police to IRGC control as needed, signaling severe responses. President Masoud Pezeshkian called for tolerance of "legitimate protests," but final security decisions lie with the supreme leader. The careful strategy now may be to tire out protesters, limit visible casualties, and avoid provoking a US attack.