In the early hours of April 19, 1964, after the collapse of Plain of Jars summit talks with the Pathet Lao had driven neutralist Prime Minister Souvanna Phouma to announce he would resign, rightist forces in Vientiane struck. General Siho Lamphouthacoul, whose 6,500-man Directorate of National Coordination police force was the instrument, induced General Kouprasith Abhay, the Military Region 5 commander, into the plot; DNC battalions seized the capital's infrastructure and arrested Souvanna Phouma and some fifteen leading officials, proclaiming a National Army Revolutionary Committee with Kouprasith as chief and Siho as deputy. A CIA analysis judged that Siho, jumping the gun before the resignation could take effect, saw in General Khanh's January coup in Saigon a model for winning American acceptance.
Instead, Washington refused: the United States reaffirmed support for Souvanna Phouma's coalition under the 1962 Geneva neutrality accords, and Ambassador Leonard Unger, returning from Saigon, confronted the generals and forced the captives' release, with Souvanna Phouma restored to office by April 23.
Researched Details
Researched
Independent research, added record by record. Hover any label for what it means.
Target identified in Coup Atlas research: Prime Minister Souvanna Phouma, arrested in the early morning of April 19, 1964 along with about fifteen leading neutralist and other officials; he was not physically harmed, was released under American pressure within days, and resumed office as prime minister.
RESEARCHED NAME
Key figures
Souvanna Phouma (neutralist prime minister, arrested and later restored)
Siho Lamphouthacoul (general, police chief whose DNC executed the coup)
Kouprasith Abhay (general, Military Region 5 commander, named chief of the revolutionary committee)
Leonard Unger (US ambassador who forced the coup's reversal)
Phoumi Nosavan (rightist strongman who stood aside)
Sources
A same day White House situation report recorded that in the early morning hours of April 19, local time, forces under General Kouprasith and General Siho arrested the neutralists including the prime minister and seized power in the name of the National Army Revolutionary Committee, following Souvanna Phouma's April 18 announcement that he would submit his resignation after the failed summit; a curfew and martial law were imposed, a statement allegedly by Souvanna Phouma relinquishing power was broadcast, and the United States issued a strong statement urging the captives' immediate release.
SOURCE REVIEWEDForeign Relations of the United States, 1964-1968, Volume XXVIII, Document 22open source ↗
The coup was committed by the policemen of the Directorate of National Coordination: a special battalion seized Vientiane's infrastructure and by 4:30 arrested Souvanna Phouma and 15 leading officials of opposed factions, the coup force emptied the neutralist headquarters safe and looted Kong Le's home, Kouprasith was chosen as successor to power with Siho his deputy, and although successful the coup was overturned five days later through US Ambassador Leonard Unger, who confronted the generals and ordered the captives released.
A CIA memorandum of April 22, 1964 judged the coup only marginally successful, its authority limited to Vientiane, and analyzed that Siho, inordinately ambitious and politically unsophisticated, jumped the gun early on the morning of 19 April before Souvanna's resignation could take effect, possibly seeing in the recent coups in South Vietnam, which Siho reportedly called similar to General Khanh's, a key to US recognition; the memorandum also scored the coup a success on one count, the effective end of the tripartite coalition.
SOURCE REVIEWEDForeign Relations of the United States, 1964-1968, Volume XXVIII, Document 33 (CIA memorandum)open source ↗
Ambassador Unger's April 19 teleconference with Secretary Rusk records Unger telling Kouprasith and Siho that the United States could not accept the morning's action and supported the Government of National Union under the Geneva framework, pressing for the detainees' release, with the generals, in Unger's description, giving the impression of badly frightened men who realized they had climbed too far out on a limb; the neutralists were released and Souvanna Phouma returned to negotiations, resuming the premiership.
SOURCE REVIEWEDForeign Relations of the United States, 1964-1968, Volume XXVIII, Document 27; restoration corroborated by Wikipedia, 1964 Laotian coupsopen source ↗
Editorial Note
DATASET VERSUS OUTCOME: the dataset codes a successful coup on April 19, 1964, and the plotters did seize the capital and the prime minister, but the takeover was reversed within about five days under American pressure, with Souvanna Phouma restored; per the Ethiopia 1960 and Gabon 1964 precedents the event is enriched as coded with the reversal flagged. Date variance: the infrastructure seizure began the night of April 18 and the arrests came in the early morning of April 19, the dataset's date, which the contemporaneous White House report supports. The lasting consequence recorded by the sources was political: the tripartite coalition effectively ended and Souvanna Phouma was pushed rightward. Keep distinct from the failed Phoumi Nosavan coup of August 4, 1964 and the January 1965 coups.
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:
Coup Atlas research identifies the target as: Prime Minister Souvanna Phouma, arrested in the early morning of April 19, 1964 along with about fifteen leading neutralist and other officials; he was not physically harmed, was released under American pressure within days, and resumed office as prime minister..
Baseline coding: Incumbent executive removed from power. Recorded leader fate: deposed; 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
“Fighting Disturbs U.S.,” by Hedrick Smith, May 16, 1964
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 →