What recent US attacks on Iran or its allies prompted the supreme leader's warning that continuing attacks would produce

The warning

Iran's Supreme Leader, Ayatollah Mojtaba Khamenei, warned that if the US keeps attacking the Islamic Republic, Iran and the "Resistance Front" hold "unforgettable lessons" for the US [1][3][4]. He issued the warning in the context of continuing US attacks and also accused the US of betraying the Islamabad memorandum [4][6]. Around the same time, he warned that Gulf powers would no longer shield US military bases in the region, saying Washington had lost its safe haven [35][37].

US attacks on Iran itself

• In late February 2026, the US and Israel launched a major strike campaign against Iran, called Operation Epic Fury in the US and Operation Roaring Lion in Israel, after nuclear talks failed to satisfy the Trump administration [7][19][20]. Targets included the supreme leader's residence, the president's compound, the National Security Council, IRGC command and control centers, missile and drone launch sites, military airfields, and Iranian air defense systems [8][21]. The campaign killed several Iranian officials, including Supreme Leader Ali Khamenei, and hit nuclear and military infrastructure [38][50].
• In mid-July 2026, the US sharply escalated by striking civilian infrastructure: bridges, railway lines, water and desalination plants, and power infrastructure [2]. Iran said the targets included six bridges in Hormozgan province, and a maritime control tower in the port of Chabahar appeared destroyed [43][44]. US Central Command said it hit Iranian maritime capabilities, missile and drone storage facilities, coastal surveillance sites, and air defense assets [24]. A seventh night of strikes cut water to villages in southern Iran [5], and the campaign ran 12 to 13 consecutive nights before the US halted it [23][41].
• The US launched new rounds after American troop deaths: one late Monday that was "designed to further degrade Iranian military capabilities used to attack commercial shipping" came after at least three US soldiers died [26], and another round on July 19 came after the death of another American service member was confirmed [40].
• The US also struck Iran in retaliation for an Iranian missile attack on US forces that the Pentagon intercepted [16][17]. During an earlier ceasefire, US forces carried out "self-defense strikes" in southern Iran against missile launch sites and Iranian boats attempting to lay mines; Iran's foreign ministry called those strikes a ceasefire violation and a sign of "bad faith and unreliability" [33][34][36].
• Around that time, President Trump threatened to strike Iranian bridges if Iran did not return to talks to end the war [49].

US strikes on Iran's allies

• Strikes hit Iranian-backed militias in Iraq, including the Popular Mobilization Forces and Kataib Hezbollah in Jurf al-Sakhar, killing fighters [10][15]. On July 28, 2026, the US and Saudi Arabia struck Iranian-backed militias in Iraq, killing at least twenty fighters and six Iranian advisers [39].
• The US attacked the Houthis in Yemen, described as Tehran's Yemeni allies, in a major air and naval campaign from March to May 2025 after Houthi attacks on shipping in the Red Sea and Gulf of Aden [22][25]. The US also carried out limited strikes on Yemen in response to Houthi attacks on shipping vessels [32]. The Houthis, in turn, threatened to broaden the war by blockading Saudi ports and publicly warned the US against attacking Iran [29][31].
• Israeli airstrikes destroyed the Hezbollah command center in Nabatieh, hitting another Iranian ally in Lebanon [11].

Pressure beyond the strikes

Washington also hit back by blockading, and later reinstating a military blockade on, ships entering or exiting Iranian ports after Tehran reimposed its blockade of the Strait of Hormuz [28][48]. Analysts noted that the ongoing US strikes on Iran could trigger a barrage of attacks from Tehran's proxy groups on American troops, allies, and interests [18].

A note on what prompted the warning

The evidence does not name a single attack that triggered the warning. Instead, it shows the warning came while the US was carrying out sustained, repeated attacks on Iran and its allies, and that Khamenei framed the "unforgettable lessons" as consequences if those attacks continue [1][3][4].