Lanna-ww2

Mae Chang Bridge (Railway Stationing: 599+848.50)^[37a1]
(aka "Mae Mo Bridge")
(N18°16.480 E99°47.435)^[37b]

The Mae Chang bridge was referred to as "Mae Mo bridge" by Allied Intel throughout the war. The Allies tied it to the general Mae Mo area, while those on the ground tied it to the waterway which it spanned, the Nam Mae Chang, and / or the railway station, a half kilometer southwest, Mae Chang, which in turn took its name from Ban Mae Chang, a small settlement about one kilometer NNE of the bridge. To complicate matters, Allied Intel was obviously aware that there was a significant bridge in the general area, but was notably vague about its location. The estimated location was actually moved around in intel reports and aerial photo requests as the war progressed, and did not appear to have been tied down until a month after it had been bombed as an alternate target.

18 September 1944

The aerial photo order below mentions one photo objective as "Memoh Bridge", though which bridge was intended in the order is unclear, for there are 21 small bridges along the railway all of which are 16-18 km (10-11 mi) south of the Mae Mo airstrips.^[37c]

^[37d]

22 September 1944

Four days later there was a photo order that included two bridges south and southeast of Pakhem.^[37e] The coordinates for Pakhem are provided in the order and place it 12 km (8 mi) southeast of the Mae Mo air facility. No photo information for the targeted bridges is described in the results.

^[37f]

25 October 1944

An attempt to photograph Memoh A/F was unsuccessful due to cloud cover; but photos were taken of the Memoh Bridge on that date:

^[37g]

On this same date, the up-to-this-point anonymous [Mae Mo] Bridge seemed suddenly much better defined:^[37h]

Transcription of applicable text:

25 Oct 44. RR bridge W of [Mae Mo] (18:16/99:43) Usable 195' single track RR bridge and probably of steel construction. Located 3 miles W of town. 800' single track siding with small station building located 1500' E of bridge.

Taking into account the different reference datum used during WWII, the broad coordinates given, N18°16 E99°43, could encompass Mae Mo station; however, there was no bridge of near that length within 3 mi west (or east) of the station. Thus, the additional information did not fit details on the ground; and the bridge remained "lost".

25 November 1944

There is no mention in the USAAF Chrono of the Allies ever bombing the Mae Mo (Mae Chang) bridge by name; however 341st BG unit records did specifically mention bombing a bridge at approximately its coordinates as an alternate target when a planned attack on the Kaeng Luang bridge was apparently aborted, as noted in a mission report:^[37i]

Seven 491st B-25s led by 1Lt. Fox departed Yangkai at 0400 hours and flew direct to attack the Kenghluang Rail and Road Bridge, IndoChina. The formation was a few miles off course when it reached the target area due to strong upper-level winds. Therefore, instead of the primary target, it attacked a railroad bridge at 18°17'N 99°47'E, about 17 miles westnorthwest of the Kengluang Railway Bridge, Thailand.

With accuracy stated only to the nearest minute coupled with a different map reference datum plus probable inaccuracies in airborne sextant work, the substitute target easily fit the Mae Chang bridge current coordinates of N18°16.480 E99°47.435.

28 December 1944: The elusive Mae Mo bridge, bombed as an alternative target in November, was finally located a month later in another Allied publication:

^[37j]

Transcription of pertinent text:

MEMOH Bridge (18°15'N 99°44'E)

(a) Fourteenth Air Force Intelligence Summary (week ending 10 January 1945) states that first air photographs (20 December 1944) reveal the 120 foot bridge east of MEMOH station as damaged and repairs on the eastern approach to be in progress.

(b) COMMENT MEMOH is a small station 16 miles east of LAMPANG. Presumably the above report refers to the 2-span structure (on a concrete pier and abutments 4 meters above water-level) about 5 miles east of MEMOH, over a branch of the MENAM WANG river. This bridge, and that at KENG LUANG, are the largest bridges on the northern railway between DEN CHAI and LAMPANG. They are of considerable importance, as there is no road between these places, and their destruction would cut off all railway traffic NW of LAMPANG, immobilizing or confining it to the stretch of line between LAMPANG and CHIANGMAI.

The bridge's length of 120 ft (37m) matches the westerly two (~120 ft (36.5m) of the actual three spans: perhaps in that remote area, the easterly most truss had been overshadowed by forest regrown more than 20 years after track installation. Other details mesh well. The bridge, or at least an approach, had been damaged; it was about 21 miles (16+5) east of Lampang; and it was the second largest bridge between Den Chai and Lampang.

The length of the comment above and its detail suggests that the report publisher, Inter-Service Topographical Department (South East Asia Command (SEAC)), wanted to tie down as firmly as possible the location of a bridge too long elusive.

In the Google Earth view below, the bridge is located in relation to the WWII Mae Mo Airstrips:

^[38]

Here a closer view shows how the bridge is located with regard to the similarly named railway station:

^[39]

And this yet closer view of the bridge allows the addition of dimensions:

^[40]

The measurements above do not compare at all well with the USAAF's reported 120 foot (36.60m) dimension, unless there had been a sequence of errors: possibly the total length of the bridge was scaled at 210 feet (instead of 218) and the numbers were then reversed (210 to 120). The designation of "two span" for three is easier to explain since the westerly span could easily be merged visually from above with the middle span.^[40a]

On the ground, the bridge is seen to be three spans: three distinctly different structures, from east to west (from right to left in the aerials just above):

1. A 30.0m long, eight panel Warren pony-truss with sway bracing and no identification plate, only a cast plate on the east entry portal stating a weight limitation, "15MT":

^[41]

2. A 24.5m "half-through" reinforced girder with a manufacturer's plate dated 2517 (1974) identifying:

Contractor: Osaka Koza (Thailand) Co, Ltd
Manufacturer: Takigami Steel Construction Co, Ltd, Handa, Japan:

^[42]

3. A 12.0m deck plate girder without identification:

^[43]

What damage, if any, might have been inflicted on the bridge during the war is unclear. The 2517 (1974) date on the middle span identifies a period when the State Railway of Thailand was upgrading structures as necessary to carry 15 MT. While the middle span was obviously replaced in that program, it is unclear if the two end spans were replaced. What with changing design standards and methods of analysis, during that same period a structural reanalysis might have determined one or both spans not to require replacement; or reinforcement of the existing structures to be sufficient. If such were the case, it is relevant to note that no damage or repairs possibly due to WW2 are obvious. Further, it is probable that span lengths probably did not change; ie, the original abutments and piers were found satisfactory and were (re)used "as is".^[44] This would strengthen the argument that Allied intel in reporting a bridge length of 120 feet was in error.

37a.^ Railway stationing per Wisarut [Bholsithi] in 2bangkok forum topic, "Ban Chang Railway Bridge, Lampang Province"(#2), 13 Feb 2014. The title was incorrect: it should have been Mae Chang, or, less correctly, Ban Mae Chang. Unfortunately, the thread was not restored after the site was destroyed by hackers.

37a1.^ ibid.

37b.^ Coordinates per Google Earth.

37c.^ BR Whyte, in The Railway Atlas of Thailand, Laos and Cambodia (Bangkok: White Lotus, 2010), shows no major bridge in that stretch of track (p 28). He specifies elsewhere (p xiii) that he lists only "major bridges" (emphasis mine), which would appear to include only structures with lengths of at least 100m.

There are lesser (simple span) bridging structures in the 95 km between the Kaeng Luang Bridge and Lampang, some of which are visible via Google Earth; 21 bridge symbols can be counted on Royal Thai Survey Department maps 4845 I and 4945 I thru IV which cover that length of railway. [«6æ]

37d.^ 21PRS Report Mission No. 4 MA 115, 18 Sep 1944 (USAF Archive microfilm reel A0878 p0441). [«6a]

37e.^ Pakhem no longer exists --- it has been absorbed by the sprawling Mae Mo lignite surface mine whose product powers the Mae Mo Power Generation Plant. However, somewhat humorously, both mapquest (at N18°20.13 E99°43.90) and Satellite Views (at N18°20.15 E99°43.92) list the location. The coordinates compare reasonably well with the photo order's N18°20 E99°48. The latter Internet source further describes Pakhem as a "City or Community: Populated place". [«6a1]

37f.^ 21PRS Report Mission No. 4 MA 118, 22 Sep 1944 (USAF Archive microfilm reel A0878 p0476). [«6b]

37g.^ 21PRS Report Mission No. 4 MA 132, 25 Oct 1944 (USAF Archive microfilm reel A0878 p0551). [«7a]

37h.^ Road and Railroad Communications Report: Asiatic Area, "Siam - Roads & Railroads", p 37
(two dates appear: 25 Oct 44 and 01 Nov 44) (Joint Intelligence Collection Agency, 01-15 Dec 1944)
(USAF Archive microfilm reel A8044 p0416). [«8]

37i.^ Courtesy of Tony Strotman (mgr, website, 
341st Bombing Group).
491st Mission C-241; Kenghluang Bridge; (Summary of narrative on Mission Report). 

The report incorrectly placed the Kaeng Luang bridge in Indochina (another report had put it in Burma --- regardless, the coordinates of the bridge were accurate, unlike many of those used in reports about the Mae Chang bridge).

Strotman cautions:

Comparing USAF Chrono dates with Mission Report dates for 341st BmGp squadrons indicates to me that some, tho definitely not all, chrono dates for CBI have been adjusted for dateline difference to reflect the America equivalent date; ie, Chrono date = CBI date minus 1.

In this instance, an editor bobbled the formula and redated the event on 26 Nov rather than 24 Nov. [«12]

37j.^ Communications in Siam, French Indo-China & Yunnan: A Monthly Summary, Part I Siam: Railways Inter-Service (?: Topographical Department (South East Asia Command (SEAC)), 01 Mar 1945), p 20 (USAF Archive microfilm reel A8021 p0178).

Coordinates given for a "Memoh Bridge", N18°15 E99°44 are not close to any significant feature. The point is about 2 km south of the rail track and 3 km ESE of Mae Mo Rail Station.

Note: weeks ending 10 Jan 1945 & 20 Dec 1944=Wed. So weekly reporting periods were Thursday through Wednesday.

The tributary to the "Menam Wang river" would be the Nam Mae Chang. Coordinates at stream center under bridge: N18°16.476 E99°47.426 (quite a contrast to the reported N18°15 E99°44).

As noted before, Whyte does not list the bridge. A previous intel description of the site which included mention of a siding is consistent with the sidings at the Mae Chang station.

The details, "on a concrete pier and abutments 4 meters above water level", suggest either the existence of an excellent quality oblique photo of the bridge, or an on-the-ground intel source, or possession of plans for the bridge. [«12a]

38.^ Google Earth image enhanced with IrfanView and annotated with Microsoft Publisher by author.

39.^ Google Earth image enhanced with IrfanView and annotated with Microsoft Publisher by author.

40.^ Google Earth image enhanced with IrfanView and annotated with Microsoft Publisher by author. Lengths per Wisarut [Bholsithi] in 2bangkok forum topic, "Ban [Mae] Chang Railway Bridge, Lampang Province"(#2), 13 Feb 2014. The thread was not restored after the site was destroyed by hackers.

40a.^ Admittedly this is pure speculation; and it is not consistent with the detailed reporting of the foundations of the bridge which imply either eyes "on the ground" or a good oblique aerial photo broadside of the bridge.

Note also that the length of the Mae Chang bridge is incorrectly recorded in the rotfaithai listing, Stations and Stops in Thailand, as 25m, while it is actually 66.5m±. The recorded distance of 25m covers the plate girder structure spanning just the stream; ironically the more prominent steel truss in the three span bridge is longer at 30m, but it does not span the stream proper.

41.^ Looking NNW; extracted from DSCF1671+1672_stitchaa.jpg of 02 Feb 2014 joined by Microsoft ICE; enhanced with IrfanView. Length scaled from Google Earth.

42.^ Looking northwest; extracted from DSCF1680b.jpg of 02 Feb 2014; enhanced with IrfanView. Length scaled from Google Earth.

43.^ Looking WNW, extracted from DSCF1694+1695-west-span.jpg of 02 Feb 2014; joined by Microsoft ICE; enhanced with IrfanView. Length scaled from Google Earth.

44.^ Program to upgrade SRT structures circa 1974 and span length probably unchanged per Wisarut [Bholsithi] in 2bangkok forum topic, "Ban [Mae] Chang Railway Bridge, Lampang Province"(#4), 13 Feb 2014. The thread was not restored after the site was destroyed by hackers.