The S&P 500 after 22 war onsets
What the S&P 500 did 1, 3, 6 and 12 months after 22 wars and military interventions began, from Korea in 1950 to the Twelve-Day War in 2025: the worst case beside the best, how far it fell first, how long it took to get back, and every episode on its own row.
· study run October 27, 2026 · data through October 26, 2026 · research, not advice
// The short answer
Twelve months after the 22 war onsets from 1950 to 2025, the S&P 500 was up a median 10.7%, and up in 16 of the 22. The worst twelve months was -43.2% (the Yom Kippur War, 1973); the best was +34.8% (the Falklands War, 1982). One month after the onset, the median was +1.3% and 15 of 22 were up.
- Median+10.7%12 months after, n = 22
- Worst-43.2%12 months after, 1973
- Best+34.8%12 months after, 1982
- Up16 of 2212 months after
In the first three months the lowest close sat a median 3.5% below the last pre-war close, and the median onset took 32 trading sessions to close back at that level. Over every session since 1950, the twelve-month median was the same 10.7%. That is the record of 22 cases. It reads history; it does not forecast what follows the next war.
// The S&P 500 after the onset
All 22 completed onsets, measured from the last close before each onset date. S&P 500 price index, gross: no dividends and no costs. A month is 21 trading sessions.
| Statistic | 1 month | 3 months | 6 months | 12 months |
|---|---|---|---|---|
| Median | +1.3% | +0.8% | +4.6% | +10.7% |
| Worst | -10.4% | -14.5% | -15.3% | -43.2% |
| Best | +15.2% | +23.5% | +20.9% | +34.8% |
| Mean | +0.7% | +1.5% | +4.6% | +8.6% |
| Up | 15/22 | 11/22 | 16/22 | 16/22 |
| Median, any session since 1950 | +1.1% | +2.7% | +5.2% | +10.7% |
| Up, any session since 1950 | 61.8% | 66.9% | 70.8% | 74.7% |
Median of the 22 Worst and best Range of the 22 Any session since 1950, median
The medians sat near an ordinary start date at one, six and twelve months, and below it at three months (+0.8% against +2.7%). The spread is the story: one month out, the worst and best onsets sat 10.4% below and 15.2% above the start; twelve months out, 43.2% below and 34.8% above. Six of the 22 were lower a year later: the Suez Crisis (-12.1%), the Yom Kippur War (-43.2%), the Iran-Iraq War (-9.3%), Panama (-3.6%), the war in Afghanistan (-26.7%) and Russia's invasion of Ukraine (-6.0%). Twelve months is long enough for other things to move the market too: the 1973 to 1974 and 2002 bear markets sit inside those numbers.
// Every episode
One row per onset, in date order. The low is the lowest close in the first 63 sessions against the last pre-war close; back to even counts trading sessions from that close to the first close at or above it after the low. No onset was dropped.
| Onset | First session | Low in 3 months | Sessions back to even | 1 month | 3 months | 6 months | 12 months |
|---|---|---|---|---|---|---|---|
| Korean WarJun 25, 1950; first session Jun 26, 1950; North Korea invades South Korea | -5.4% | -12.9% session 15 | 57 | -10.0% | +1.6% | +4.1% | +11.7% |
| Suez CrisisOct 29, 1956; Israel invades Sinai; Britain and France follow | +0.3% | -4.1% session 22 | 26 | -4.0% | -2.9% | -0.5% | -12.1% |
| Bay of PigsApr 17, 1961; US-backed invasion of Cuba | +0.5% | -3.0% session 6 | 14 | +0.7% | -2.4% | +2.5% | +1.9% |
| Gulf of TonkinAug 2, 1964; first session Aug 3, 1964; US escalation in Vietnam | -0.2% | -2.2% session 18 | 29 | -1.6% | +1.9% | +5.3% | +2.7% |
| Six-Day WarJun 5, 1967; Israel against Egypt, Syria and Jordan | -1.5% | -1.5% session 1 | 2 | +1.2% | +4.3% | +5.2% | +11.2% |
| Cambodian CampaignApr 29, 1970; US and South Vietnamese forces enter Cambodia | +1.9% | -13.7% session 20 | 83 | -9.3% | -3.3% | +4.4% | +29.5% |
| Yom Kippur WarOct 6, 1973; first session Oct 8, 1973; Egypt and Syria attack Israel; the oil embargo follows | +0.3% | -16.1% session 42 | 1,505 Sep 20, 1979 | -3.9% | -10.7% | -15.3% | -43.2% |
| Soviet invasion of AfghanistanDec 24, 1979 | +0.1% | -7.7% session 63 | 102 | +5.4% | -7.7% | +6.4% | +26.2% |
| Iran-Iraq WarSep 22, 1980; Iraq invades Iran | +0.9% | -4.4% session 6 | 10 | +2.6% | +3.4% | +5.0% | -9.3% |
| Falklands WarApr 2, 1982; Argentina invades the Falklands | +1.2% | -5.8% session 55 | 99 | +2.7% | -4.5% | +5.8% | +34.8% |
| GrenadaOct 25, 1983; US invasion | +0.3% | -2.6% session 37 | 49 | +0.5% | 0.0% | -4.8% | +0.8% |
| PanamaDec 20, 1989; US invasion | +0.1% | -5.7% session 28 | 61 | -1.0% | -0.8% | +4.9% | -3.6% |
| Iraq invades KuwaitAug 2, 1990 | -1.1% | -16.9% session 50 | 131 | -10.4% | -14.5% | -4.1% | +9.1% |
| Desert StormJan 17, 1991; the air war against Iraq begins | +3.7% | never below | 0 | +15.2% | +23.5% | +20.6% | +33.1% |
| Kosovo WarMar 24, 1999; NATO strikes on Yugoslavia | +0.5% | never below | 0 | +7.7% | +5.8% | +3.6% | +18.4% |
| War in AfghanistanOct 7, 2001; first session Oct 8, 2001; US and allied strikes begin | -0.8% | -1.4% session 2 | 3 | +2.9% | +8.7% | +4.3% | -26.7% |
| Iraq WarMar 20, 2003; the US-led invasion begins | +0.2% | -3.0% session 8 | 10 | +2.2% | +15.6% | +17.4% | +28.4% |
| LibyaMar 19, 2011; first session Mar 21, 2011; NATO-led intervention | +1.5% | -1.1% session 61 | 65 | +2.0% | -0.6% | -4.9% | +10.2% |
| CrimeaFeb 27, 2014; Russian forces seize Crimea | +0.5% | -1.6% session 32 | 35 | +0.2% | +3.5% | +8.4% | +14.4% |
| Russia invades UkraineFeb 24, 2022 | +1.5% | -7.7% session 60 | 118 | +7.0% | -6.7% | -2.0% | -6.0% |
| Israel-Gaza warOct 7, 2023; first session Oct 9, 2023; the Hamas attack of October 7 | +0.6% | -4.4% session 15 | 19 | +1.3% | +10.6% | +20.9% | +33.5% |
| Twelve-Day WarJun 13, 2025; Israel strikes Iran; the US joins on June 21 | -1.1% | -1.3% session 5 | 7 | +3.3% | +8.9% | +14.2% | +25.0% |
| 2026 Iran warFeb 28, 2026; first session Mar 2, 2026; US and Israeli strikes on Iran; in progress, not in the 22 | 0.0% | -7.8% session 21 | 30 | -7.8% | +10.2% | +12.1% | not yet |
The first session after an onset was small more often than not: a median +0.3%, with 13 of 22 inside 1% either way. The exceptions were Korea, down 5.4% on the first session, and Desert Storm, up 3.7%. Some windows overlap: Desert Storm began inside the year after Iraq invaded Kuwait, and the 2026 Iran war began inside the year after the Twelve-Day War.
The 2026 Iran war, in progress. US and Israeli strikes on Iran began on Saturday, February 28, 2026, so the first session was Monday, March 2. As measured on October 26, 2026, the S&P 500 was 7.8% below its last pre-war close after one month, 10.2% above it after three months and 12.1% above after six; its low came on the 21st session and it closed back at the pre-war level on the 30th. Twelve months: not yet. It is not one of the 22 and sits in no average.
// Oil wars and the rest
Ten of the onsets disrupted or threatened oil supply: Suez, the Six-Day War (an Arab oil embargo was declared and soon faded), Yom Kippur, Iran-Iraq, Kuwait, Desert Storm, Iraq, Libya, Ukraine and the Twelve-Day War. The other twelve did not.
| Group | Onsets | 1-month median | 12-month median | Up at 12 months | Worst 6 months | Median low in 3 months |
|---|---|---|---|---|---|---|
| Oil-disrupting onsets | 10 | +2.1% | +9.6% | 6/10 | -15.3% | -3.5% |
| Other onsets | 12 | +0.6% | +13.0% | 10/12 | -4.8% | -3.7% |
| All 22 | 22 | +1.3% | +10.7% | 16/22 | -15.3% | -3.5% |
The oil group's twelve-month median was lower and its worst cases were deeper, with the Yom Kippur War and the Kuwait invasion both in it. Its first month was stronger, led by Desert Storm. For oil supply shocks measured by the oil price itself, see Oil shocks and the S&P 500.
// Method and data
- The list. 22 onsets of a war or military intervention from 1950 to 2025, each involving the US or a major oil producer, or a Middle East war: invasions, the first strikes of a campaign and the first day of open fighting. The list and every date were fixed before any return was computed, and no onset was added or dropped after. It is a judgment list, not a count of every conflict.
- The date. The first day of hostilities. Where that fell on a weekend, a holiday or after the New York close, the first session that could react is the next one; the anchor is always the last close before the onset date. Other studies often use the date tension began instead, so their figures differ.
- Stock returns. Daily closes of the S&P 500 price index, from the anchor to 21, 63, 126 and 252 sessions later. Gross: no dividends and no costs. Before March 1957, when the S&P 500 itself began, the series is its predecessor index.
- Low and recovery. The lowest close in sessions 1 to 63 against the anchor, and the first close at or above the anchor after that low. An onset that never closed below the anchor in those 63 sessions counts as 0 for both.
- Baseline. The same horizons over every session from January 3, 1950 that has a full window (19,074 to 19,305 sessions).
- In progress. The 2026 Iran war sits only in its own row, outside every average, as measured on October 26, 2026.
- Where it ran.
query_warehousequeries over QuantGPT's MCP on October 27, 2026, with prices through October 26, 2026. Every forward return, median and up count was checked against QuantGPT'sevent_studytool on the same dates, and they matched.
// Run your own
- Your own dates. QuantGPT's
event_studytool runs this kind of study in one call over MCP: give it event dates and a ticker, and it anchors each event on the last close before the event date, measures forward returns at 21 trading sessions a month, and sets them beside the same horizons over every session in its price history (from 1928 for the S&P 500, so its comparison figures differ a little from this page's 1950 baseline).
Connect Claude · Connect ChatGPT - World events, live. The terminal's event desk sets each new event against the record of its
kind, war onsets among them. The lesson on world events needs no account.
Lesson 4: World events - The data. Every figure on this page, one row each, with its sample size and a source line.
Download the CSV - New to QuantGPT? 3 days free on QuantGPT or QuantGPT Pro, cancel any time.
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// Questions
How do stocks usually move after a war starts?
Across 22 war onsets from 1950 to 2025, the S&P 500 was up a median 1.3% one month after the last pre-war close (15 of 22 up), 0.8% after three months (11 of 22 up), 4.6% after six months (16 of 22 up) and 10.7% after twelve months (16 of 22 up). Over every session since 1950, the twelve-month median was also 10.7%. The range was wide: twelve-month results ran from -43.2% to +34.8%. These are S&P 500 price returns, with no dividends and no costs.
How far does the market fall after a war begins, and how long does recovery take?
In the first three months after the 22 onsets, the S&P 500's lowest close sat a median 3.5% below the last pre-war close, and the median onset took 32 trading sessions to close back at that level. The deepest low was -16.9%, after Iraq invaded Kuwait in 1990. Two onsets never closed below the pre-war level in those three months: Desert Storm in 1991 and the Kosovo War in 1999. The slowest recovery followed the Yom Kippur War of 1973: 1,505 sessions, until September 1979.
Do wars that disrupt oil hit stocks harder?
In this sample the 10 oil-disrupting onsets had a twelve-month median of +9.6%, up in 6 of 10, against +13.0% and 10 of 12 for the other 12. The worst six months among the oil onsets was -15.3% (the Yom Kippur War), against -4.8% for the rest. Ten and twelve cases are small samples.
What was the worst case?
Twelve months after the Yom Kippur War began in October 1973, the S&P 500 was 43.2% lower; the oil embargo and the 1973 to 1974 bear market followed it. The worst one month and three months came after Iraq invaded Kuwait in 1990: -10.4% and -14.5%. Six of the 22 were lower twelve months later.
Does this forecast what stocks will do after the current conflict?
No. It is the record of 22 past onsets, and twelve months out they ranged from -43.2% to +34.8%. It reads history; it does not forecast. The 2026 Iran war sits in its own row, outside every average. QuantGPT is a research tool, not investment advice.
Where does the data come from?
Daily closes of the S&P 500 price index from QuantGPT's warehouse, through October 26, 2026; before March 1957, when the S&P 500 itself began, the series is its predecessor index. The onset dates come from the public record and were fixed before any return was computed. The study ran on October 27, 2026 over QuantGPT's MCP, and every figure on this page is in the free CSV.