The confrontation between Israel and the United States on one side and Iran on the other has moved into open warfare. To understand why it reached this point, it helps to separate two tracks that have been building for decades: U.S.–Iran relations (revolution, sanctions, and the nuclear dispute) and Israel–Iran relations (a long proxy conflict that repeatedly risked turning direct).
This article explains the historical drivers that led to the current situation, without turning it into a debate piece. Where possible, it focuses on the stable, well-documented milestones that most analysts cite as “load-bearing” causes of today’s crisis.
Contents
What happened in late February 2026
In the early hours of 28 February 2026, Israel announced a “pre-emptive” strike on Iran, and multiple outlets (including Reuters) reported U.S. strikes underway as the confrontation escalated rapidly.
By 1 March 2026, Reuters and other major outlets reported continued strikes on Tehran and other targets, with Iran responding through missile/drone attacks across parts of the region.
The conflict also widened into Gulf shipping lanes and infrastructure. Reuters reported drone/strike incidents and tanker damage near Oman and around the Strait of Hormuz—an immediate sign that “regional spillover” is not hypothetical.
Those are the triggers. The “why” sits deeper, in the decades-long structure of hostility, deterrence, and failed containment.
U.S.–Iran: the long arc
The modern U.S.–Iran relationship is largely shaped by a single rupture: the 1979 Iranian Revolution and the hostage crisis that followed, which poisoned political trust for generations and made “Iran” a central adversary in U.S. regional strategy.
From there, the relationship developed into a cycle: U.S. sanctions and pressure; Iranian regional influence via the Revolutionary Guard and aligned groups; periodic escalations; and repeated diplomatic attempts to “cap” the conflict through nuclear agreements or indirect negotiations.
The nuclear file became the most important strategic lever. The 2015 nuclear deal (JCPOA) temporarily reduced tensions by restricting parts of Iran’s nuclear program in exchange for sanctions relief, with international monitoring at the center of the framework. The IAEA’s safeguards timeline provides a useful anchor for how that monitoring and compliance logic evolved over time. IAEA safeguards timeline (JCPOA and after).
After the U.S. withdrew from the JCPOA in 2018, the nuclear dispute re-entered a sharper phase of escalation and mistrust, with each side blaming the other for non-compliance and bad faith. Over time, that dispute became inseparable from military planning: diplomacy no longer felt like a stable off-ramp, and “preventing a nuclear outcome” became a justification that could be invoked for force.
If you want a neutral, high-level chronology of the U.S.–Iran relationship milestones (1953 onward), the Council on Foreign Relations timeline is a clear reference point: U.S. Relations With Iran (timeline).
Israel–Iran: from hostility to proxy war to direct confrontation
Israel and Iran did not always stand on opposite sides. After 1979, however, Iran’s leadership adopted a posture of ideological and strategic hostility toward Israel, while Israel increasingly treated Iran as its most serious state-level threat—especially as Iran expanded support for Hezbollah and other aligned groups, and as the nuclear program progressed.
For decades, the conflict largely ran through proxies and covert action: weapons pipelines, intelligence operations, cyber activity, and strikes on aligned forces in third countries. This “shadow war” repeatedly threatened to become direct—and in recent years, it began to do so more openly, with direct exchanges and wider regional impacts.
By the time the late-February 2026 strikes occurred, the Israel–Iran track already had the ingredients of a direct war: a long proxy conflict, repeated escalatory cycles, and a nuclear dispute that both sides framed as existential.
Why the U.S. and Israel are aligned in this war
The U.S.–Israel partnership is one of Washington’s deepest security relationships: Israel was designated a major non-NATO ally in 1987, and the two governments later signed a ten-year U.S. security assistance Memorandum of Understanding in 2016 worth $38 billion. Alongside decades of intelligence and defense cooperation, this reflects a strategic commitment to Israel’s security and regional deterrence, reinforced by close coordination on missile defense and a long tradition of bipartisan political backing.
In a crisis with Iran, the partnership tends to translate into operational alignment because both countries view Iran’s regional posture as a central driver of instability: Tehran’s Revolutionary Guard and its external networks support armed groups that have threatened Israel directly and targeted U.S. forces and partners across the region. At the same time, U.S.–Iran relations have been structurally hostile since the 1979 revolution and the U.S. embassy hostage crisis, followed by decades of sanctions, sporadic clashes, and repeated breakdowns in diplomacy around Iran’s nuclear program.
Israel–Iran relations moved from ideological hostility into a long “shadow war” and proxy conflict (especially via Hezbollah and other Iran-aligned actors), repeatedly escalating through covert action, strikes outside Iran, and direct missile/drone exchanges. When trust collapsed further after the nuclear deal era and each side’s red lines hardened—Israel’s focus on preventing a nuclear-capable Iran and Iran’s insistence on deterrence through regional proxies—the U.S.–Israel alliance became the bridge that connected the two conflict tracks.
Why it boiled over now
History doesn’t force a war, but it can make war easier to start. In this case, four drivers stacked over time:
- Nuclear escalation and collapsing trust: the JCPOA breakdown left fewer credible diplomatic off-ramps, raising the role of force as a “solution.”
- Regional proxy infrastructure: years of Iranian influence-building made the conflict geographically wider than Israel–Iran alone.
- Deterrence failure: repeated tit-for-tat actions eventually tested red lines until one side chose a large-scale strike.
- Gulf spillover risk: once retaliation touches shipping lanes and nearby states, escalation becomes harder to contain.
That is why today’s war is not just “about one event.” It is the collision of two long histories—U.S.–Iran and Israel–Iran—amplified by the nuclear dispute and by a region where escalation rarely stays local once missiles and drones begin to fly.
If you want the immediate, practical travel and safety implications of this escalation, you can also see our related update here: Iran Crisis No-Fly Zone: What Travelers Need to Know
