Pai Bridge

The Pai River bridge is often cited as the most visible evidence of the presence of Japan's Army in Northern Thailand during WWII.
But the statement is incorrect. This website attempts to resolve that error, as well as other misconceptions about the period.

Lanna-ww2

Japan in Northwest Thailand during World War II

N18°21.5
E99°24.4[1]
Hang Chat[1a] Landing Ground
(Th: ห้างฉัตรท่าอากาศยาน / Jp: ハンチャツ滑走路)

Lampang Province
Page 1 of 3
near Hang Chat
RR Station on
Northern Route
Sta 654.85 [2]

 

Text Notes

 

Hang Chat: Summary

Hang Chat Landing Ground was the westerly air facility satellite to the Lampang Airfield Group of the Imperial Japanese Army Air Force (IJAAF). The site's two approximately parallel north-south runways were located about 12 km by air northwest of Lampang Railway Station (the reference point used by Allied intelligence during WW2), and about 14 km by air from the Lampang runway. Constructed by the Japanese in 1944-1945, no aircraft was ever observed there. After the war, the runways quickly melted back into their rice paddy heritage and are invisible today.

[2a]
Hang Chat LG location NOL


August 1944

Discovery of a Japanese Army air facility under construction at Hang Chat was first announced by Allied intelligence in August 1944. The Allied unit providing the "photographic evidence", presumably a photographic reconnaissance squadron (PRS), was not identified.[2å]

[2b]
First report, written, on Hang Chat

TRANSCRIPT (smoothed, comments and emphasis mine):[2β]

Thailand:

Photographic evidence during the period under review [presumably August 1944] has only been obtained on three airfields in Thailand. Of these [Chiang Mai] and Lampang were observed to be undergoing considerable development in the form of increased dispersal, surfacing, and general maintenance. The third site is a new airfield, now officially named [Hang Chat] Landing Ground, located 6¾ miles northwest of Lampang Railway Station. Although this site is not considered operational as yet, it was in a fairly advanced stage of construction and significantly enough has two strips both lying N-S and about 900 yards apart. On each strip, clearing has taken place over a length of about 1750 yards.

This development at the northern extremity of the Thailand line of airfields has been expected and it is the opinion of this Headquarters that, when weather conditions permit reconnaissance further south to Bangkok and beyond, many additional air facilities will be observed, particularly in the Bangkok area.


The newly discovered installation was then mentioned in several different parts of the same airfield report, with much supplemental information.

This section added approximate coordinates:

[2c]
New airfields list Aug 1944

TRANSCRIPT of description:

6¾ miles northwest of Lampang Railway Station, 4¼ miles east of Ban [Hang Chat] Railway Station. Situated north of Lampang-[Chiang Mai] Railway line.


An approximate location map was added:

[2d]
New landing ground map


Its aircraft shelters were tallied --- just 2:

[2e]
Shelters at Hang Chat


17 August 1944: Text from another section generally summarized the various pieces of information above:

[2f]
Hang Chat status rpt 17 Aug 1944

And provided the following additional facts:

• The title ends with (J), indicating that Allied intelligence believed
   that the air facility was being developed solely by the Japanese.

• The information was obtained on 17 August.

• The last paragraph clarified: "No aircraft were visible and it is
   doubtful whether the strips are yet serviceable."


31 August 1944: And finally, still from the same report, yet more information:

[2g]
First full page rpt on Hang Chat

Note that distances and approximate bearings from three points are given:

• 6¾ miles northwest of Lampang railway station
• 4½ miles east of Ban Hang Chat railway station
• 3½ miles from Ban Bau railway station

The last station named, Ban Bau (?), does not match any currently listed station. However the other two exist, and specified radii intersect at a point about two miles east-northeast of the location as finally determined in the 16 March 1945 sketch shown on the next page.


September 1944

Though its easterly runway never became serviceable, Hang Chat was planned to have a configuration different from other airstrips in northwest Thailand: it was to have two approximately parallel runways separated by about 400 yards (365 m). An insight into the logic of this approach, a multi-runway air facility, was offered in the September 1944 Airfield Report:

[2h]
Multi-runway tactic

Relevant text of above (emphasis added):

. . . the Japanese considered that single strips were a sufficient provision so long as they had reason to believe that the Allies could not wage an offensive campaign from the air supported by the threat of ground forces. At the present time, however, the enemy have been forced to accept the challenge of the growing Allied strength in this theatre, and the measures taken by them have assumed several novel aspects. The multiple strip airfield is one of them.

It has been described as taking the form of two or more strips or runways sited some distance apart but incorporated within an extensive network of taxi tracks and dispersal areas. Generally speaking the direction of those runways or strips is more or less common to each individual site, for instance at Myingyen 2 strips are aligned N-S and one NNW-SSE, while at Laihka the three strips veer from NNW-SSE to NE-SW. The significance of this is that they are not aligned in order that landing facilities may be available in a variety of wind directions but are intended for simultaneous employment for one or a combination of the following reasons:

(a) The operation of a large number of aircraft at one time
      from a restricted locality.

(b) In order to ensure that, under any period of sustained
     operations, serviceability can be maintained without
     interruption for maintenance purposes. At least one strip
     could be undergoing general overhaul while the others
     were in use.

(c) To provide an additional insurance against concentrated
     Allied bombing attacks. The [probability] of all runs at a      multiple strip airfield being rendered unusable at one time
     would be somewhat remote. Thus the danger of based
     aircraft being grounded through cratered runways is      progressionally removed as additional strips are added.


22 September 1944
: Aerial photo objectives included "Area NW of Lampang", followed by the "RR (railroad) strip W of Lampang". Photos recorded as actually taken include "A/F 4 miles NW of Lampang". The handwritten note above that reads: "Lampang NW A/F". All of which could only have been the facility at Hang Chat. This is the first record of aerial photography of Hang Chat. Because of the detailed information available prior to this date, it can be assumed that aerial photo coverage of the facility was available from another PRS. Aerial photography of Hang Chat's sister facility, Mae Mo, was recorded at least as early as February 1944.


Hang Chat aerial 22 Sep 1944[3]


26 September 1944
: Work was noted as continuing, with airstrips not yet functional:

[3a]
Sep 1944 text on Hang Chat


22 October 1944: Surfacing of the eastern strip was observed to be in progress. Construction effort would concentrate on the eastern strip through 15 December:

[3b]
22 Oct 1944 report on Hang Chat

Text (smoothed):

[Hang Chat] Landing Ground (J)

Activity: Infrequent cover during the month failed to disclose the presence of any aircraft. (22 Oct 1944)

Development: Construction work on this landing ground continues. Surfacing of the easterly strip and development of dispersal systems is in progress. Several barracks type huts have been constructed 1700 yards west of the strips. (22 Oct 1944)


25 October 1944: Allied planners anticipated the Japanese army, on retreating from its failed invasion of India, would "hold its ground" in Burma with support from bases in Thailand. As a consequence, the planners introduced the concept of the "Thailand Line of Airfields", which the planners also realized might themselves require defense:

[3β]
Thai line of airfields

Text of above (smoothed):

Thailand:

As in Burma considerable post-monsoon reclamation work is proceeding. Development of the Thailand Line of Airfields, an illustration of which is given overleaf [see below], continues and it is now clear that full preparations are being made for basing and operating aircraft from this sector as and when Allied pressure increases in Burma. This strategic line is capable of providing complete air cover to Rangoon and the Irrawaddy Valley.

The immediate zone for providing air cover to Northern Burma is the Shan Plateau area. The secondary zone will be the [Chiang Mai] Group at the Northern end of the Thai line.

[3c]
Thai line of airfields

Text circled above (smoothed):

Hangchat Landing Ground

• 2 Strips. North-south. 1750 & 1750 yards. Rolled earth.
• Category C [liable to become unserviceable after rains].
• 6 aircraft shelters.
• A new site in an early stage of development.


02 November 1944: While photos were requested only for "Lampang", Hang Chat was included as "Lampang NW A/F":


Hang Chat aerial 02 Nov 1944 [4]


11 November 1944: Japanese Army work continued:

[4a]
11 Nov 1944 note


Photos taken included both "Lampang A/D" and "Lampang NW A/D"; the latter could be assumed to have been Hang Chat, though "A/D", ie, "air drome" or "aerodrome", was usually reserved for larger facilities such as that at Lampang:

Hang Chat aerial 11 Nov 1944[5]


15 November 1944: While the format used for the 31 August 1944 report was followed, this report was printed rather than being mimeographed:

[5a]
15 Nov 1944 Hang Chat page

Items of significance that were updated:

• Clarification of the facility's limitation weather-wise:
     Dry weather only. Heavy rains during southwest monsoon
     period, May-October.

• Various "temporary airfield buildings" had been erected.

• Clarification of the name of the unknown railway station,
   3½ miles distant: Ban Mau. Unfortunately there is no
   station with that name in the area.


27 November 1944
: Curiously, description of photos taken continue to describe "Lampang NW A/F" though the name, "Hangsat", had been repeatedly used in an August report:


Hang Chat aerial 27 Nov 1944[6]


15 December 1944: The continuing work began adding revetment walls:

[6a]
15 Dec 1944 note on Hang Chat


31 December 1944: Allied intelligence viewed the site as a base for future Japanese operations over Burma; this assumed, erroneously, that Japan could populate the field with aircraft, pilots, ground personnel, and provide adequate support, etc:

[6b]
31 Dec 1944 front page report with map

31 Dec 1944 report page 2

31 Dec 1944 report page 3


 

Revision List
Rev
Date
Description
0
2012 Dec 05
First published on Internet
1
2014 Jan 05
Content materially expanded.

 

 

 

These pages were composed to be best viewed with Google Chrome.

See Key for interpreting page content.

Revision list. See bottom of Text column on this page.

1.^ Source: USAAF data fitted to Google Earth.

1a.^ During WWII: "Hangsat". Earliest postwar maps found to date use "Hang Chat".

Note: not listed in Air America's Air Facilities Data Thailand 432, 1971.

2.^ Whyte, BR, The Railway Atlas of Thailand, Laos, and Cambodia (Bangkok: White Lotus, 2010), p 28.

2a.^ "Terrain" map from Nations Online Project: Searchable Map and Satellite View of Thailand using Google Earth Data. Annotation by author using Microsoft Publisher.

 

 

 

 

 

 

2å.^ The unit would apparently not have been the 21PRS for which flight records are available (and presented here as applicable).

2b.^ Airfield Report No. 25, Aug 1944, "Comments on Current Airfield Development", p II
(USAF Archive microfilm reel A8055 p0840).

Because of the quantity of information provided in this airfield report which introduces Hang Chat, its sequence has been changed from page number to time-ordered. Undated material is presented first, with dated material following, in chronological order.

2β.^ Texts are occasionally transcribed herein when there are complaints about illegibility. Spelling of locations generally reflects current usage.

 

 

 

 

 

 

 

 

2c.^ Airfield Report No. 25, Aug 1944, "New Airfield Sites", p VI
(USAF Archive microfilm reel A8055 p0909).

 

 

 

 

 

 

 

 

 

 

 

2d.^ Airfield Report No. 25, Aug 1944, "Japanese Enemy Airfields", unnumbered page (USAF Archive microfilm reel A8055 p0855).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2e.^Airfield Report No. 25, Aug 1944, "Aircraft Shelters", p VI
(USAF Archive microfilm reel A8055 p0909).

 

 

 

 

2f.^ Airfield Report No. 25, Aug 1944, "Record of Airfield Activity and Development", p 7 (USAF Archive microfilm reel A8055 p0862).

 

 

 

 

 

 

 

 

 

 

 

2g.^ Airfield Report No. 25, Aug 1944, unnumbered page (USAF Archive microfilm reel A8055 p0880).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2h.^ Airfield Report No. 26, Sep 1944, "Multiple Strip Airfields", p (iii)
(USAF Archive microfilm reel A8055 p0970).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.^ 21st Photographic Reconnaissance Squadron (hereafter 21PRS) Report Mission No. 4 MA 118, 22 Sep 1944 (USAF Archive microfilm reel A0878 p0476).

The flight reports here record aerial photo coverage of Hang Chat Airstrips (Hangsat Landing Ground) by only the 21st Photographic Reconnaissance Squadron (21PRS). Other coverage probably exists, but it does not appear to have been released to this point in time. Reports aside, no WW2 era photos of the facility have been found as yet (other than the extremely poor quality mimeographed (?) copy published on 31 January 1945and shown on the next page).

3a.^ Airfield Report No. 26, Sep 1944, "Record of Airfield Activity and Development", p 10 (USAF Archive microfilm reel A8055 p0988).

 

 

 

 

3b.^ Airfield Report No. 27, Oct 1944, "Record of Airfield Activity and Development", p 9 (USAF Archive microfilm reel A8055 p1019).

 

 

 

 

 

 

 

 

 

 

 

3β.^ Airfield Report No. 27, Oct 1944, "Comments on Current Airfield Development", "Thailand", p ii (USAF Archive microfilm reel A8055 p0998).

The "Chiang Mai Group" is nowhere else defined.

 

 

 

 

 

 

 

 

 

3c.^ Airfield Report No. 27, Oct 1944, "Thailand Line of Airfields", unnumbered page (USAF Archive microfilm reel A8055 p0999).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.^ 21PRS Report Mission No. 4 MA 139, 02 Nov 1944
(USAF Archive microfilm reel A0878 p0568).

 

 

 

 

 

 

 

 

 

 

 

 

4a.^Airfield Report No. 28, Nov 1944, "Record of Airfield Activity and Development", p 8 (USAF Archive microfilm reel A8055 p1133).

 

 

 

 

5.^ 21PRS Report Mission No. 4 MA 140, 11 Nov 1944
(USAF Archive microfilm reel A0878 p0586).

 

 

 

 

 

 

 

 

 

 

 

 

 

5a.^ Airfield Report No. 28, Nov 1944, "Thailand Line of Airfields", unnumbered page (USAF Archive microfilm reel A8055 p1088).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.^ 21PRS Report Mission No. 4 MA 170, 27 Nov 1944
(USAF Archive microfilm reel A0878 p0621).

 

 

 

 

 

 

 

 

 

 

 

6a.^Airfield Report No. 29, Dec 1944, "Record of Airfield Activity and Development", p 7 (USAF Archive microfilm reel A8055 p1181).

 

 

 

6b.^ Siam (Thailand) List of Airfields and Seaplane Stations, (Washington: GPO, 1945), unnumbered pages (USAF Archive microfilm reel A1285 p1157).