Issue 073 - Military history - Historical frequency
How historically unusual is a major power's foreign military campaign?
When a major power launches or joins an overseas military campaign, the event can feel singular. This challenge asks how often the United States, USSR/Russia, China, Britain, and France have done something comparable since 1945.
Public systems and economicsAbout 1 minute
Sources checked October 9, 2026. Figures and circumstances may have changed.
The problem
From 1945 to 2025, across the United States, USSR/Russia, China, Britain, and France, about how many separate foreign military campaign involvements occurred?
Define what counts, then convert the count into campaigns per decade and compare it with the smaller subset involving ground invasions or major ground deployments.
Because Fermi problems target an order of magnitude, I normally use no more than two significant digits and write most calculations in scientific notation; the Fermi reference explains both conventions.
Grounding facts
The Military Intervention by Powerful States project, or MIPS, studies the United States, Britain, China, France, and Russia/USSR from 1945 to 2003. It defines a military intervention as an official deployment of at least 500 regular military personnel using, or prepared to use, force against a foreign adversary for immediate political objectives.
Under that definition, MIPS codes 126 major-power military interventions from 1945 to 2003. It reports 35 U.S. interventions, 29 French interventions, and 17 Chinese interventions, with Britain and Russia/USSR making up the remaining 45.
A separate Military Intervention Project focused only on the United States finds almost 400 U.S. interventions since 1776, with about half between 1950 and 2019. That broader U.S.-only universe is a useful warning: counts explode when the definition includes smaller deployments, shows of force, evacuations, and repeated operations.
After checking sources
Checked answer and calculation
The strongest direct check is MIPS:
five-power interventions, 1945-2003
= 126 interventionsThat period is about 58 years, or 5.8 decades:
interventions per decade
~= 126 / 5.8
~= 22 per decade across all five powersExtending from 2003 to 2025 requires judgment because the MIPS dataset stops in 2003. A conservative continuation adds the 2003 Iraq War and later U.S., British, French, and Russian campaigns such as Libya, Syria, Mali/Sahel operations, Georgia, Ukraine, and other substantial deployments. That pushes the 1945-2025 total into the neighborhood of:
checked scale, 1945-2025
~= 1.3 x 10^2 to 1.8 x 10^2
~= about 150 campaign involvementsAcross eight decades, that implies:
campaigns per decade across all five powers
~= 150 / 8
~= 19 per decadeSo, under a MIPS-style definition, major-power foreign military interventions are not once-per-generation anomalies. They are recurring events, averaging roughly two per year across the five powers. That does not mean each is equally important; scale, duration, casualties, objectives, legality, and consequences still matter enormously.
The ground-invasion subset is narrower. RAND's U.S. ground-intervention work uses a ground-troop threshold of at least 100 person-years, and MIPS itself includes air, naval, and ground interventions. A rough rule of thumb is that major ground invasions or large ground deployments are perhaps one-third to one-half of the broad MIPS-style count:
ground-invasion / major-ground subset
~= 50 to 80 cases across 1945-2025
~= 6 to 10 per decade across the five powersThe exact number depends on whether you count colonial wars, regime-maintenance operations, peace enforcement, coalition partners separately, and repeated interventions in the same country as one campaign or several. But the key scale lesson survives: remembered big wars badly undercount how often major powers have used force abroad.
Before checking sources
Matt's original estimate
This is the unverified estimate Matt wrote before checking sources, not the checked answer.
I don't have a strong recollection of major international military campaigns involving those nations in the last 8 decades. I came up with:
ww1
vietnam
korea
iraq
afghanistan
iran
ukraine x3
For each nation I count individual nation involvement:
US 6
Russia 5
CN 0
UK 2
FR 2
So that's about 15 total involvements by each of these nations in the events I recall in the last 8 decades, so this is a bottom figure, and it seems the US and Russia are the most belligerent while China is the least.
It looks across the 5, they average about 2 international military campaigns per decade as a bottom figure, and individually they average about 0.4 per decade.
Reasoning score
Matt's reasoning score: 55 / 100
Higher is better: earn points for useful facts, a sound reasoning approach, correct math, and a final estimate close to the sourced answer. The owl meter shows percent full of it: 100 minus the reasoning score.
Useful facts: 10/30. The remembered list was very incomplete and included World War I, which falls outside the 1945-2025 window. The China intuition was directionally right, but the U.S., Britain, and France were badly undercounted.
Reasoning approach: 15/30. Counting country-involvements and dividing by decades was a reasonable structure, but the definition was too narrow and depended almost entirely on remembered headline wars.
Math: 10/10. The arithmetic followed cleanly from the remembered count.
Final estimate: 20/30. About 15 involvements is roughly a factor of ten below the checked MIPS-style scale, so it is barely within the broad order-of-magnitude band but misses the real frequency.
Post-check reflection
Matt's reflection
Well my recollection of conflicts is very US-centric, and terribly incomplete. Turns out my intuition that China is not terribly belligerent on the international scene was right, at least when counting military conflicts, and I wasn't giving the US enough credit compared to France and the UK. I really should recalibrate on those points.
Recommended memory peg
For post-1945 major-power interventions, remember about 20 MIPS-style interventions per decade across the five permanent-security-council powers. Big remembered wars are only the visible tip of a much larger intervention record.
Reader results
Bars show how submitted estimates sort into the answer choices from the gut-check prompt.