Coup Atlas Research Database
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81106251978ConspiracyForeign-backed coup

Cambodia, 1978 — foreign-backed coup conspiracy

Cambodia (KHM)Southeast Asia, AsiaJune 25, 1978

Event Summary

This entry is coded 25 June 1978, corresponding to the Eastern Zone uprising and purge in Democratic Kampuchea, in which So Phim, the pro-Vietnamese commander of the Khmer Rouge Eastern Zone, was suspected by Pol Pot of plotting a Vietnam-backed rebellion. The Eastern Zone, bordering Vietnam, was run by cadres more closely connected to Hanoi than to the Party Center, and its uniforms and conduct set it apart from Pol Pot's loyalists. As border war with Vietnam intensified, Vietnamese officials conducted secret meetings with So Phim to plan a military uprising, and after eastern-zone troops failed to resist Vietnamese incursions, Pol Pot labeled the region a nest of traitors.

From January 1978 the Center purged the Eastern Zone, sending cadres to Tuol Sleng and killing or replacing commanders through the spring. So Phim, summoned to a meeting and realizing it was a trap, went into hiding and committed suicide on 3 June 1978 as Center forces encircled him; his family was killed. The purge escalated into mass killings across the zone.

Researched Details

Researched

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

Target identified in Coup Atlas research: Pol Pot crushed the Eastern Zone and So Phim; the surviving cadres fled to Vietnam and later helped overthrow the Khmer Rouge in 1979
RESEARCHED NAME
Key figures
Pol Pot (Khmer Rouge leader who ordered the purge)
So Phim (pro-Vietnamese Eastern Zone commander, target)
Vietnamese officials (foreign backers of the planned uprising)

Sources

Vietnamese government officials conducted secret meetings with So Phim, the Khmer Rouge leader in the Eastern Military Zone, to plan a military uprising backed by Vietnam, and Pol Pot labeled the region a nest of traitors.
SOURCE REVIEWED Military Wiki: Cambodian-Vietnamese War open source ↗
So Phim was secretary of the East Zone until he refused to carry out the genocide designed by Pol Pot, a refusal that led to his suicide in June 1978.
SOURCE REVIEWED Wikipedia: So Phim open source ↗
In 1978, after eastern-zone troops failed to resist a Vietnamese incursion, So Phim was accused of being an ally of Hanoi, a massive purge led by Ke Pauk was ordered, and on 3 June 1978 So Phim committed suicide while encircled by Pol Pot's forces.
SOURCE REVIEWED Alamy caption (dated primary photo record) open source ↗
Summoned to a meeting he realized was a trap, So Phim went into hiding, and when center soldiers arrived instead of Pol Pot, he committed suicide and the soldiers killed his family, while the center embarked on a large-scale purge of the eastern zone.
SOURCE REVIEWED Wikipedia: Khmer Rouge open source ↗

Editorial Note

Coded 25 Jun 1978 (foreign-backed coup) corresponds to the So Phim / Eastern Zone affair, the Vietnam-backed uprising Pol Pot suspected; So Phim's suicide is dated 3 June 1978 and the purge ran spring through summer 1978, so the 25 June coding sits within the broader Eastern Zone rebellion and purge. Verified as the So Phim affair (foreign backer = Vietnam). First Cambodia record in the run.

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
81106251978

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

Outcome and Target

Coup Atlas research identifies the target as: Pol Pot crushed the Eastern Zone and So Phim; the surviving cadres fled to Vietnam and later helped overthrow the Khmer Rouge in 1979.

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

The Globe and Mail

“Vietnam, CIA Plotted Coup, Cambodia Says,” June 26, 1978

The Guardian

“Viet Coup Thwarted Says Cambodia,” June 26, 1978

The Sun

“Cambodia Says It Foiled Coup Plot,” June 26, 1978

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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