Coup Atlas Research Database
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23503111975AttemptedMilitary coup

Portugal, 1975 — military coup attempt

Portugal (PRT)Southern Europe, EuropeMarch 11, 1975

Event Summary

On 11 March 1975 the former president Antonio de Spinola and allied right-wing officers attempted a coup to halt the leftward march of the Portuguese revolution, months after Spinola had resigned the presidency following his failed silent majority bid. Paratroopers from the Tancos air base moved against the leftist First Light Artillery Regiment in Lisbon, a stronghold of the radical Armed Forces Movement, in an operation meant to break the power of the revolutionary left. But the coup was a fiasco.

The Tancos troops, discovering they were being used against fellow soldiers, mutinied; workers and loyal units surrounded the attackers, and the rising collapsed within hours. Spinola fled the country, first to Spain and then to Brazil. Far from turning back the revolution, the failed coup radicalized it further: the Armed Forces Movement dissolved existing structures, set up a Supreme Revolutionary Council with sweeping powers, and launched a wave of nationalizations of banks and major industries, deepening the leftist Ongoing Revolutionary Process of 1975.

Researched Details

Researched

Independent research, added record by record. Hover any label for what it means.

Target identified in Coup Atlas research: The revolutionary government crushed Spinola's March 1975 coup; Spinola fled and the revolution radicalized
RESEARCHED NAME
Key figures
Antonio de Spinola (former president, coup leader who fled)
Armed Forces Movement leftist officers (targets who prevailed)
Tancos paratroopers (who mutinied)

Sources

On 11 March 1975 the right-wing led by Spinola attempted a coup by attacking left-wing soldiers in Lisbon, the coup petered out, and Spinola fled to Brazil.
SOURCE REVIEWED Socialist Worker, Timeline of the Portuguese revolution open source ↗
On 11 March paratroopers from the Tancos airbase moved against RAL 1, one of the most left-wing army units, but the troops at Tancos mutinied when they found out they were being used against other units, and Spinola fled.
SOURCE REVIEWED Socialist Alternative, Revolution in Portugal 1974 open source ↗
After the failed coup the whole structure of the MFA was dissolved and a Supreme Revolutionary Council was set up with full legislative powers, and the banks were occupied and nationalized.
SOURCE REVIEWED Socialist Alternative, Revolution in Portugal 1974 open source ↗
Spinola's tentative involvement in the rightist counter-revolution on 11 March 1975, after which he fled to Brazil, was an example of his changed allegiances following the Carnation Revolution.
SOURCE REVIEWED Wikipedia, Antonio de Spinola open source ↗

Editorial Note

Date match to the 11 March 1975 Spinola coup attempt. Dataset codes it a military coup with leader unharmed, reflecting the revolutionary government surviving; the coup instead radicalized the revolution. Well documented. Third and last of the three Portugal records in this batch, completing the 1974 to 1975 revolutionary sequence (Caldas da Rainha, silent majority, Spinola coup).

Cross-Reference

Datasets agree. At least two of the three reference datasets we check against carry this event, and none of them disagrees about its date or its result.

Identifiers for finding this same event in the other datasets:

Cline Center id
23503111975
Albrecht/Koehler/Schutz (CAM) id
CAM-235-1975-03-11

How the match is made is described in crossref-report.md.

Outcome and Target

Coup Atlas research identifies the target as: The revolutionary government crushed Spinola's March 1975 coup; Spinola fled and the revolution radicalized.

Baseline coding: Coup attempt failed to remove the incumbent. Recorded leader fate: remained in office; not physically harmed. The baseline file does not name individual targets; researched names are kept in a separate layer.

Baseline Dataset Citation

Cline Center Coup d’État Project Dataset, v2.2.2
Peyton, Buddy, Joseph Bajjalieh, Michael Martin, and Andrea Gerald. 2026. Cline Center Coup d’État Project Dataset. Cline Center for Advanced Social Research. V.2.2.2. February 17. University of Illinois Urbana-Champaign. doi: 10.13012/B2IDB-9651987_V10
⚑ This citation establishes the coded baseline record; use the claim-level sources above for the researched narrative.

Baseline Source-Document Entries

CSP

Named in the baseline source document; no article citation was recorded.

Luttwak

Named in the baseline source document; no article citation was recorded.

Wikipedia

New York Times

“News Summary and Index The Major Events of the Day,” March 13, 1975

This is the citation trail carried by the baseline dataset, grouped by outlet and rejoined from the line-wrapped original. Coup Atlas has not independently re-checked every document; read the original before citing a specific claim. URLs the import damaged beyond safe repair are shown as plain text and listed in citations-report.md. How this list is built →

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