Russia and Iran have a troubled history despite their current alliance

MOSCOW — Russian President Vladimir Putin hosted his Iranian counterpart Friday for the signing of a broad pact between Moscow and Tehran.

The Kremlin says the ''comprehensive strategic partnership'' agreement between Putin and Iranian President Masoud Pezeshkian will take their cooperation to a new level.

What to know about the relationship between Russia and Iran:

Historic rivals become allies

Russia and Iran fought wars in the 18th and 19th centuries, with the Russian Empire capturing broad territories in the Caucasus and the Caspian region previously controlled by Persian rulers. In the early 20th century, Russian troops occupied large parts of northern Iran, but the 1917 Bolshevik Revolution ended their presence. In World War II, the Soviet Union and Britain invaded Iran, which still evokes painful memories in Tehran.

Tensions ran high in the Cold War, when Tehran was a U.S. ally under the Shah of Iran. After his ouster in the 1979 Islamic Revolution, leader Ayatollah Ruhollah Khomeini castigated the U.S. as the ''Great Satan,'' and denounced the USSR as the ''Lesser Satan.''

Russia-Iran ties warmed after the USSR's demise in 1991. Moscow became an important trade partner and a key supplier of weapons and high tech to Iran, which faced isolation from sweeping international sanctions.

Russia was part of the 2015 deal between Iran and six nuclear powers offering sanctions relief for Tehran in exchange for curbing its atomic program and opening it to broader international scrutiny. Moscow offered political support to Iran when the U.S. unilaterally withdrew from the agreement during President Donald Trump's first term.

Allies in Syrian civil war in bolstering Assad

After a civil war in Syria erupted in 2011, Russia and Iran pooled efforts to shore up Bashar Assad's government against Turkey-backed rebels seeking his ouster. In 2015, Russia launched a military campaign in Syria, joining Iran and its proxies, that helped Assad re-establish control in most of the country.

With Moscow preoccupied with fighting in Ukraine, and Iran facing challenges from Israel, they failed to prevent a swift collapse of Assad's rule last month after a lightning opposition offensive, and he fled with his family to Russia.

How Russia and Iran cooperate

Iranian leaders give strong political support to Putin, echoing his arguments for justifying the conflict.

Tehran likely hopes to secure financial and defense promises from Moscow for its tattered economy after the collapse of the 2015 nuclear deal and amid increasing pressure in the Middle East.

Assad's downfall was a major blow to Tehran's self-described ''Axis of Resistance'' in the region after Israel's punishing offensives against two militant groups backed by Iran -– Hamas in Gaza and Hezbollah in Lebanon. Israel attacked Iran directly twice, and Israeli officials claimed the raids took out Tehran's Russia-supplied S-300 air defense systems.

Iran wants Russian long-range air defense systems and other weapons. It has hoped to get Russia's advanced Su-35 fighter jets to upgrade its aging fleet hobbled by sanctions, but Moscow only provided a few Yak-130 trainer jets in 2023.

Trump's policy of ''maximum pressure'' on Iran heralds more trouble for Tehran as he prepares to start his second term on Monday. This month, he left open the possibility of the U.S. preemptive airstrikes on Iranian nuclear sites. Iran insists its nuclear program is peaceful, but some officials increasingly suggest it could pursue atomic weapons.

Putin described the deal as a ''real breakthrough" while Pezeshkian praised it as a ''new chapter of strategic relations'' helping expand trade ties and boost the ''level of security cooperation.''

The 20-year treaty that could be extended further covers all areas -– from trade and military cooperation to science, education and culture. It doesn't envisage mutual assistance in case of aggression, but obliges both countries not to offer any military or other assistance to an aggressor attacking one of them.

Iranian Foreign Minister Abbas Araghchi told state TV that while the pact covers defense and security cooperation, ''this is a complete and comprehensive treaty, not one focused on a specific purpose, such as a military alliance.''

Healing rifts, lifting suspicions

Despite the official rhetoric, the nations' troubled history makes many Iranians suspicious about Russia. Kremlin efforts to balance courting Tehran while staying friendly with Israel adds to the uneasiness.

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