Coup Atlas Research Database
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23503151959ConspiracyMilitary coup

Portugal, 1959 — military coup conspiracy

Portugal (PRT)Southern Europe, EuropeMarch 15, 1959

Event Summary

The dataset records an event coded as a military conspiracy in Portugal on 15 March 1959, corresponding to the Cathedral Coup (Golpe da Se), a plot by army officers who stored weapons in the Lisbon cathedral. Prepared by figures from the National Independent Movement (Movimento Nacional Independente) linked to opposition presidential candidate General Humberto Delgado, whose 1958 campaign against the Salazar regime had galvanized hopes for change, the coup was defeated in March 1959 by Salazar and the PIDE secret police. It was the first of several failed attempts to overthrow the Estado Novo dictatorship, and its failure was followed by a significant wave of PIDE arrests through 1959 and 1960 that drove many oppositionists into exile.

Researched Details

Researched

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

Target identified in Coup Atlas research: Salazar and PIDE defeated the plot and the Estado Novo dictatorship endured
RESEARCHED NAME
Key figures
Antonio de Oliveira Salazar (Portuguese dictator, target)
Army officers of the National Independent Movement (plotters)
General Humberto Delgado (opposition figurehead linked to the plot)

Sources

In March 1959 Salazar and PIDE defeated the Cathedral Coup, a plot by army officers who stored weapons in the cathedral.
SOURCE REVIEWED Portugal Resident, Opposition to Salazar's Regime open source ↗
The Cathedral Coup (Golpe da Se) took place on 11 March 1959, prepared by figures from the National Independent Movement also linked to Delgado, and its failure was the first of several that led to coup attempts aimed at overthrowing the dictatorship.
SOURCE REVIEWED Cambridge Core, A Sense of Hopelessness (Contemporary European History) open source ↗
PIDE, the Estado Novo's political police, made a significant number of arrests between 1959 and 1960, driving several oppositionists to leave the country.
SOURCE REVIEWED Cambridge Core, A Sense of Hopelessness (Contemporary European History) open source ↗

Editorial Note

Near-exact date match: the coded 15 March 1959 is a few days after the ~11 March 1959 Cathedral Coup. Well documented as the Golpe da Se. First discrete named Portuguese plot in the dataset run, continuing the Portugal thread from the earlier Salazar-era record.

Cross-Reference

Only one dataset carries it. One of the three reference datasets we check against carries this event; the others do not list it. That is not a contradiction — the datasets cover different periods and use different thresholds — but it means the record has had less outside corroboration.

Identifiers for finding this same event in the other datasets:

Cline Center id
23503151959

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

Outcome and Target

Coup Atlas research identifies the target as: Salazar and PIDE defeated the plot and the Estado Novo dictatorship endured.

Baseline coding: Plot discovered and disrupted before execution. 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

New York Times

“Portuguese Trial Adjourned,” July 7, 1960

Manchester Guardian

“31 arrests in Portugal: PLOT TO ’ALTER PUBLIC ORDER’,” May 8, 1959

Washington Post and Times Herald

“Plot to Upset Salazar Smashed, Portugal Says: Rumors Confirmed,” May 8, 1959

Christian Science Monitor

“Portugal Says Plot Crushed in March: Silence Explained,” May 7, 1959

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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