Sources

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Most of the coastlines and national outlines are originally Natural Earth, except China's, which is derived from the Republican province sheet below and nothing else; China's provinces are the real ones of 1928–45; Korea comes from a map of the period rather than from modern units; the princely states of India were georeferenced by hand from a 1931 atlas; and the occupied zone and the line of control are traced from period maps and are approximations, as they say on the map itself.

Boundaries and coastlines

• Natural Earth, 1:10m cultural vectors. Most of the coastlines and national outlines outside China, and the base for the frame. Public domain — Natural Earth's terms state the data may be used in any manner, including modifying the content and design, and that no permission is needed.
  github.com/nvkelso/natural-earth-vector
• ENP-China — Chinese provincial boundaries, 1928–1945. Now only used for the coastline of China. Originally the provinces of China were used from this dataset but on further investigation, the version we had seems to show interior provinces (such as Shaanxi frontier along the Yellow River) significantly distant from where it should be. I decided to keep the coastlines from this layer for convenience and then redo the provinces from historical maps (see below). Christian Henriot (June 16, 2021). Administrative map of Republican China: Provinces (1912-1928). Elites, Networks and Power in modern China. Retrieved August 24, 2026 from https://doi.org/10.58079/o8ls
• 最新世界大地図 - David Rumsey Historical Map Collection, Fuchida, Tadayoshi, Saishin sekai daichizu: Shina zendo narabi fukin daichizu. Oshū gensei daichizu (1940) List No. 13462.003. This map was used to re-trace all the republican period provinces of China.
• 中華民國新地圖 交通及物產詳記 (1936 [earlier version 1928]) - HKUST Library . This map was also consulted in tweaking the republican period provinces.
• 中華民國新地圖 (1947) - Academia Sinica. This map was also consulted in tweaking the republican period provinces.
• geoBoundaries ADM1 and ADM2. The provinces ceded to Thailand in 1941, the northern Malay states, Burma by division, Kengtung by district, the Indian, Japanese and Philippine first-level units, Siam's changwat, and Bangkok's fifty khet — which are gathered by tools/fetch_tha_bangkok.py into Phra Nakhon and Thonburi, two provinces until 1971 that no modern first-level unit can tell apart. CC BY 4.0.
  github.com/wmgeolab/geoBoundaries · Runfola, D. et al. (2020), "geoBoundaries: A global database of political administrative boundaries", PLoS ONE 15(4): e0231866.
• Korean Provinces - I confess, I have had this dataset for some time and don't remember where I found it. If anyone is able to identify the source, I would gladly cite it.
• The princely states of India, 1931. Georeferenced from the atlas volume of the Imperial Gazetteer of India, 1931. Digital South Asia Library
  
• French India - French India primarily done from Paul Palet's 1889 Inde. Nouvel atlas des colonies Françaises par Paul Pelet, 1889, No 14. A. Challamel, Éditeur, 5 rue Jacob, Paris. Gravé par R. Hausermann, Paris, Imp. Lemercier et Cie. Portuguese India. Also consulted 1920s Survey of India 1:126,720 map of Karikal. Sheet 58N/NE. and Territoire de Yanaon (en rose), un des cing Établissements français dans l'Inde, mieux connus sous le nom de Comptoirs de l'Inde (1932). Also consulted French Settlement of Chandernagore Surveyed Season 1870-71 with a portion of the River Hoogly, and of the Country on its Left Bank (1872)
• Portuguese India - Goa traced from 1892 Districto de Goa found here. Damão, Dandrá and Avely Nagar drawn in consultation with this map.
• Nepal, Afghanistan, Sikkim and Bhutan, 1931. From Natural Earth, and tweaked in consultation of the above 1931 Imperial Gazetteer sheet.
• British Weihaiwei and French Kwangchowan - Traced in consultation with several historical maps.
• OpenStreetMap Coastlines. Zooming in provides finer coastlines of the Ryukyus, the Bonins, the Volcano and Izu Islands, and of Micronesia and Melanesia — the Marianas, Palau, the Carolines with Truk, Ponape and Kusaie, the Marshalls, the Bismarcks, Bougainville, the Solomons, the Louisiades and the Gilberts — and the names of nineteen hundred islands in them, with the group each belongs to. These come from OSM coastline sources.
  © OpenStreetMap contributors, available under the Open Database Licence. Map data and any derived database are ODbL; the coastline geometry drawn here is a Produced Work under that licence. OSM Coastlines

Rivers

• Natural Earth, 1:10m rivers and lake centrelines. The Yangtze and the Yellow River; Indian rivers. Public domain. Two hand-drawn tails were needed: Natural Earth's Yangtze centreline stops about 200 km short of the sea, and its Yellow River stops short of the Gulf of Chihli.
• The 1938–47 course of the Yellow River is redrawn from the channel map first seen at disasterhistory.org but originally from a map at this article: Archived on Archive.org.

Japanese Occupations and the line of control

• The starting point of inspiration was the line of control drawn in Andrew Gordon's map in his textbook A Modern History of Japan, and modifications below were then begun from there to fit the December, 1942 date.
• The Pacific mandates — Japan's South Seas Mandate, Australia's Territory of New Guinea and the British mandate over Nauru — are traced from the Outline Chart of the World map produced by the U.S. Navy Hydrographic Office. Held at Princeton University, call number G3201.A1.1927.H9 and may be viewed online here.
• Manchukuo is traced from 滿洲國地圖 1935, published by the research section of the South Manchuria Railway Company (南滿洲鐡道株式會社資料課). A digital version is available online at the International Research Center for Japanese Studies (Nichibunken) library, no. 004863874 and can be viewed here.
• The Kwantung Leased Territory is traced by hand from the above 1935 sheet.
• Japanese Occupation of China (Approximate) and Resistance Base Areas - This layer is drawn from the Chinese atlas of the Sino-Japanese War 武月星主編，《中國抗日戰爭史地圖集：1931–1945》 (Wu Yuexing, ed., Historical Atlas of China's War of Resistance against Japan, 1931–1945) p199 for 1941-2 years.
• The North China Area Army's own security map, September 1942 — the alternative reading offered in Layers. 付図第五「北支那方面軍占拠地域内治安概況（昭和十七年九月中）」, an appendix to 防衛庁防衛研修所戦史室 編『北支の治安戦＜2＞』(戦史叢書 第50巻, 東京: 朝雲新聞社, 1971), held by the National Institute for Defense Studies and readable there in full. Traced and published as kmlawson.github.io/1942-occupation-map. See this blog post on Frog in a Well for more discussion. Two of the sheet's three categories are areas and are drawn here: pacified 治安地区, and un-pacified 未治安地区. The third, semi-pacified 準治安地区, is what the sheet leaves blank, and it is left blank here, so unshaded ground inside north China is not securely controlled by anyone, according to that map.
  nids.mod.go.jp/military_history_search/SoshoView?kanno=050
  
• Mengchiang and Outer Mongolia are traced from the above mentioned 支那全土並附近大地圖 (Shina zendo narabi fukin daichizu · Ōshū gensei daichizu), a Japanese sheet of 1940. Various Chinese language histories of Japanese occupied inner Mongolia were then consulted to find settlements that are likely to have been occupied around 1942. This was then made visually distinct from the full claimed territories for Mengjiang which includes unoccupied areas to the west of Baotou.
• The line of control in south China - These are pieced together from various textual sources on the extent of the occupation. The line of control is drawn approximately to include places where Japanese forces were known to be garrisoned or where "puppet" administrations were set up. These areas can definitely be improved.
• Saharat Thai Doem — Kengtung and the trans-Salween Shan states — follows the map by Xufanc on Wikimedia Commons, CC BY-SA 4.0, taken district by district rather than cut off with a straight line. File:Saharat_Thai_Doem_map.png shows the territory Japan actually granted rather than everything Thailand claimed in the Shan and Karenni states.

Projection. Web Mercator, on a Pacific-centred frame running 66°E–206°E and 13°S–55°N — British India to Pearl Harbor, Sakhalin to northern Australia. Longitudes are normalised to 0–360 so the map is continuous across the antimeridian.

Software

Georeferencing of various historical maps done with QGIS. Website code created with Anthropic's Claude, with Konrad Lawson at the prompt. No third-party JavaScript libraries: the page is plain HTML, CSS and JavaScript, and the build scripts use only the Python standard library.

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