Coup Atlas Research Database
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14505161951SuccessfulAuto-coup

Bolivia, 1951 — auto-coup

Bolivia (BOL)South America, AmericasMay 16, 1951

Event Summary

On May 16, 1951, Bolivian President Mamerto Urriolagoitia annulled the results of the May 6 general election and handed power to a military junta to keep the opposition Nationalist Revolutionary Movement (MNR) out of office, a maneuver known as the mamertazo. The MNR's Victor Paz Estenssoro had won a plurality but not the absolute majority required, which under the constitution would have thrown the choice to Congress. Rather than allow that, Urriolagoitia resigned and turned the government over to a military junta headed by General Hugo Ballivian, which then dissolved Congress and voided the election by decree on June 7.

Urriolagoitia went into exile. The repressive junta lasted less than a year before the MNR seized power in the April 1952 Bolivian National Revolution and Paz Estenssoro finally took office.

Researched Details

Researched

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

Target identified in Coup Atlas research: Mamerto Urriolagoitia, President of Bolivia (resigned and handed power to a military junta; went into exile)
RESEARCHED NAME
Key figures
Mamerto Urriolagoitia (outgoing president who staged the mamertazo)
Hugo Ballivian (general who headed the junta)
Victor Paz Estenssoro (MNR election winner denied office)

Sources

After Victor Paz Estenssoro of the MNR won the most votes on 6 May 1951 without an absolute majority, a military junta assumed the government on 16 May with General Hugo Ballivian as president, and Congress was dissolved and the election annulled by decree on 7 June.
SOURCE REVIEWED Wikipedia, "1951 Bolivian general election" open source ↗
Urriolagoitia refused to hand power to Paz Estenssoro and instead installed the head of the military, General Hugo Ballivian, as president to keep the MNR out; this coup against the democratic order became known as the mamertazo of 1951.
SOURCE REVIEWED Wikipedia, "Mamerto Urriolagoitia" open source ↗
The government of President Urriolagoitia voluntarily relinquished executive power to the army, which appointed the junta, after the MNR candidate won a plurality but not the majority required under the constitution.
SOURCE REVIEWED U.S. Department of State, Foreign Relations of the United States, 1952-1954, Vol. IV, Document 136 open source ↗
Urriolagoitia resigned on 16 May 1951 and handed the government to General Hugo Ballivian, who a few days later abrogated the elections.
SOURCE REVIEWED Encyclopedia.com, "Urriolagoitia, Mamerto (1895-1974)" open source ↗

Editorial Note

Sources agree the sitting president annulled the election and handed power to a Ballivian-led junta on 16 May 1951 (the mamertazo). The Cline dataset codes this as an auto-coup with the leader fleeing the country, matching Urriolagoitia's resignation and exile. Two Wikipedia articles, a primary FRUS document, and Encyclopedia.com were read directly. The junta was overthrown by the April 1952 revolution, a separate record.

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
14505161951
Albrecht/Koehler/Schutz (CAM) id
CAM-145-1951-05-16

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

Outcome and Target

Coup Atlas research identifies the target as: Mamerto Urriolagoitia, President of Bolivia (resigned and handed power to a military junta; went into exile).

Baseline coding: Incumbent executive removed from power. Recorded leader fate: deposed; fled the country. 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
Open dataset DOI ↗
⚑ This citation establishes the coded baseline record; use the claim-level sources above for the researched narrative.

Baseline Source-Document Entries

Luttwak

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

Wikipedia

en.wikipedia.org/wiki/Hugo_Ballivi%C3%A1n

New York Times

“World News Summarized,” May 17, 1951
“Bolivia Explodes Again,” May 17, 1951

Chicago Tribune

“Bolivia Fights Revolt, 18 Die in La Paz Battle,” April 10, 1952

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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Related Records

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