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Lima Site 85 (Phou Pha Thi)
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Lima Site 85, located atop the 1,789-meter Phou Pha Thi mountain in Houaphanh Province, was one of the most secret and strategically vital military installations during the Second Indochina War. From 1966 to 1968, the U.S. Air Force operated a sophisticated TACAN (Tactical Air Navigation) site here to guide bombing missions over North Vietnam during night and poor weather. The site was considered inaccessible due to the sheer cliffs surrounding the peak, which is sacred to the local Hmong and Yao people. However, in March 1968, North Vietnamese commandos successfully scaled the cliffs and captured the base in a significant surprise attack. This battle resulted in the highest loss of U.S. Air Force ground personnel in a single action during the entire war. Today, the location is a somber historical site, though access is limited due to unexploded ordnance and its remote geography. It remains a powerful symbol of the Secret War in Laos and the extreme conditions under which military operations were conducted.
- Location: Laos
- Nearby: Nam Et-Phou Louey (18 km)
Best time to visit & climate
The most pleasant time to visit is Feb, Mar, Oct.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg °C | 15 | 17 | 21 | 23 | 24 | 24 | 24 | 23 | 22 | 20 | 17 | 14 |
| Rain mm | 16 | 9 | 32 | 62 | 111 | 109 | 172 | 201 | 106 | 69 | 25 | 13 |
📋 Practical info
Visiting
Visiting this remote historical battlefield is extremely difficult due to the rugged terrain and its location in a politically sensitive mountainous region. It is strictly an outdoor experience for adventurous travelers.
Typical hours
There are no official opening hours or designated entrance gates for this remote mountainside location. Daylight hours are the only safe time to attempt any exploration of the surrounding landscape.
Photography
Photography of the natural landscape and any remaining historical markers is generally possible, but be cautious. Always avoid photographing local military installations or border patrol areas.
Time needed
A challenging trek to the vicinity can easily take a full day or more, depending on the starting point and weather conditions. Proper preparation is essential for navigating the steep paths.
Combine with
Combine this arduous journey with a visit to the broader Houaphanh Province, taking time to explore local villages or the famous Viengxay caves if logistical arrangements permit.
Getting there
Access is typically extremely limited and usually requires hiring a local guide with extensive knowledge of the terrain and regional permits. Do not attempt to hike this remote area independently.
Insider tip
Because unexploded ordnance (UXO) remains a significant danger in Laos, never stray from clearly marked trails and strictly follow the advice of experienced local guides at all times.
Geography
Facts
- Located on the 1,789-meter summit of Phou Pha Thi mountain.
- Served as a top-secret U.S. tactical navigation site for bombers.
- Overrun in March 1968 by North Vietnamese commandos.
- The peak was believed to be naturally protected by 300-meter cliffs.
- Site of the largest ground loss for the US Air Force in the war.
- Considered a highly significant site in the history of the Secret War.
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Sights in the town Lima Site 85 (Phou Pha Thi) (1)
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Frequently asked questions
What was Lima-Site 85?
A strategically important US radar post on Phou Pha Thi mountain during the Secret War in Laos.
What happened here in March 1968?
North Vietnamese special forces stormed the base in a spectacular climbing operation, resulting in heavy US casualties.
Is the site accessible to tourists today?
Yes, recently the mountain has become accessible again, but it requires a permit and often local military or guide accompaniment.
Why is Phou Pha Thi considered a sacred mountain?
Local ethnic groups believe that powerful spirits dwell on the summit, which is why the site was historically avoided.
What can still be seen of the base today?
One can still find debris from radar installations, helicopter landing pads, and monuments to the fallen soldiers.
Lima Site 85 (Phou Pha Thi): where is it located?
Lima Site 85 (Phou Pha Thi) is located in Laos.
Lima Site 85 (Phou Pha Thi): when is the best time to visit?
The most pleasant time to visit is Feb, Mar, Oct.
Lima Site 85 (Phou Pha Thi): why is it worth visiting?
Lima Site 85, located atop the 1,789-meter Phou Pha Thi mountain in Houaphanh Province, was one of the most secret and strategically vital military installations during the Second Indochina War.
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