Corps of Royal Engineers
Known as the Royal Engineers (RE) or commonly as the Sappers.
The Signals Service was part of the Royal Engineers up until the time of the creation of the separate Royal Corps of Signals in June 1920.
- 1716 Corps of Engineers consisting of officers only formed by the Board of Ordnance
- 1772 Soldier Artificer Company comprising other ranks raised in Gibraltar
- 1787 officer corps became the Royal Corps of Engineers. Corps of Royal Military Artificers comprising NCOs and private raised
- 1797 Gibraltar company absorbed by the Corps of Royal Military Artificers
- 1812 Corps of Royal Military Artificers became Corps of Royal Sappers and Miners
- 1856 Royal Engineers and Royal Sappers and Miners became a unified corps as the Corps of Royal Engineers
- 1862 1 April, the three engineer corps of the East India Company:- Bengal Engineers, Bombay Engineers and the Madras Engineers were amalgamated into the Corps of Royal Engineers absorbing the British officers and men .
History of the Corps of Royal Engineers has been published in twelve volumes, the first four being available online, refer below. The other volumes are
- Volume V: The Home Front, France Flanders and Italy in the First World War. Volume VI: Gallipoli, Macedonia, Egypt and Palestine 1914-18. Volume VII: Campaigns in Mesopotamia and East Africa, and the inter-war period, 1918-38. Volumes 5-7 edited by H.L. Pritchard, published 1952. Note: Volume VI does not include information about Signals as "The history of their work is being produced by the Royal Corps of Signals themselves", so it is likely the other volumes for the WW1 period similarly do not include information about Signals.
- Volume VIII: Campaigns in France and Belgium, 1939-40; Norway, Middle East, East Africa, Western Desert, North West Africa, and activities in the U.K. by Major-General R. P. Pakenham-Walsh.
- Volume IX: Campaigns in Sicily and Italy; the War Against Japan; North-west Europe, 1944-45; minor and non-operational areas; post-war, 1945-48 by Major-General R. P. Pakenham-Walsh. Both published 1958. Note: War Against Japan includes c 200 pages regarding India, Burma, Hong Kong and Malaya. 
- Volume X: 1945-1960. Volume XI: 1960 to 1980. Volume XII: 1980-2000.
The Work of the Royal Engineers in the European War 1914-1919. For online editions, refer below. Available at the British Library:
- Water supply. [Containing 9 maps showing the] Water supply in France] (1921) UIN: BLL01004844114 ;
- Work under the Director of Works (France) (1924) UIN: BLL01006788368 ;
- Miscellaneous. The organization and expansion of the Corps, 1914-18. Organization of engineer intelligence and information. Camouflage service. Concrete defence works and factories. Forward communications. Machinery, workshops, and electricity. Anti-Aircraft searchlights. Inundations. Schools. Compiled by Colonel G. H. Addison. 1926. BLL01007769877
The flash, also known as a pagri (puggaree) badge, was generally affixed to the pagri on the sun helmet. The Royal Engineers had three styles of flashes. The first was a rectangular one with blue and red in equal halves - blue to the front. This was introduced in 1884 during the Sudan Campaign. During the 2nd Boer War they adopted a plain yellow flash to better distinguish them from the RA and then in 1902 changed to a red rectangular flash with two narrow royal blue lines near the outer edges i.e. red/blue/red/blue/red.
It is difficult to identify Foreign Service (Wolseley Pattern) helmet flashes because the type of black & white film used at that time distorted coloration. 
- Royal Engineers Wikipedia
- Corps of Royal Engineers regiments.org
- Royal Engineers Museum, Library and Archive Gillingham, Kent.
- The Institution of Royal Engineers (InstRE) publishes “The Royal Engineers Journal” and Corps Histories
- Military Engineers in India in the 20th Century from Royal Engineers and Engineers of the British Empire and Commonwealth
- "Sir Thomas Hungerford Holdich 1843 – 1929" His Life Story, Chapters 1-5 cover his time in India. (click on the drop down menu). He became a Royal Engineer and he was sent to India on attachment to the Survey Department. His first campaign was in Bhutan in 1865. This led to his permanent appointment to the Survey Department. He subsequently served in the 2nd Afghan War. he was appointed as Surveyor to the Historical Boundary Commission which was to settle the boundary between Russia and Afghanistan, and then Chief Commissioner to settle the boundary between Persia and Baluchistan He was involved with the 1898 campaign against the Afridis, but soon had to retire as he had reached the age of 55. The Holdich Family History Society (retrieved 14 April 2014). Thomas Holdich Wikipedia. For online books, refer below.
- Brigadier-General Sir William Danvers Waghorn (1867-1936). Commissioned as a Royal Engineer 1887, joined the Public Works Department, Railways in India. Served in the Boer War as Deputy Assistant Director of Railways, and the Western Front, WW1 as Chief Engineer of XVII Corps. Retired 1924 India. Sample page from Biographical Dictionary of Civil Engineers in Great Britain and Ireland: Volume 3: 1890–1920. ICE Publishing 2014. icevirtuallibrary.com
- From the Main Index of "A Newman Family Tree", select H E M Newman. He was commissioned into the Corps of Royal Engineers on 19 December 1919 and posted to India in 1924 as an officer of the Madras Sappers and Miners. He was in India until 1929 and again in India and Burma 1936-1943. The site includes his Memoirs (152 pages pdf), the article Waziristan 1937-1939 ( 9 page pdf) by Lieut Colonel H E M Newman The Royal Engineer Journal Volume 95, number 2, 1984 and this html extract which covers parts of the period 1918-1946. The two latter links are included in the Memoirs.
- "Why Britons walked warily in Waziristan" by Alastair Lawson 21 April 2008 news.bbc.co.uk with photographs In 1919, a young British army officer, Francis Stockdale, was deployed to Waziristan. He was a temporary R. E. officer and served late 1919 to Dec 1921.
- "Marching on to Laffan's Plain" by Alan Shaw , the experiences as an officer of the Corps of Royal Engineers `"The Sappers", first in the UK, then for nearly four years with the imperial Indian Army in Central India, Ceylon and the Burma campaign. Chapter 3 At the very end of this chapter, the author received orders to proceed to India or Burma. Ch 4 Arrived in India May 1942, Ch 5, Ch 6, Ch 7, Ch 8, Ch 9 , Ch 10, Ch 11, Ch 12, Ch 13, Ch 14 BBC's WW2 People’s War
- "The War Diary Of A Royal Engineer With The Forgotten Army". Staff-Sergeant George Philip Benbow (Phil) Vaughan in India and Burma. Part 1: 13 March 1943 to 31 July 1944, Part 2: 1 August 1944 to 1 June 1946 BBC’s WW2 People’s War
- In India: The Postwar Years 1945 to 1947 by former Sergeant Donald C. Thyer Royal Engineers Survey. "Sunset on the Raj" britains-smallwars.com/India, now archived.
- "Health Hazards …Stationed in India" by former Sergeant Donald C. Thyer, Royal Engineers Survey 1945-1947 britains-smallwars.com, now archived
- Inland Water Transport and Docks Reubique.com. The article mentions that this section of the Royal Engineers was founded in 1914 and was later responsible for alternate transportation during World War One in various theatres of war - including Mesopotamia where personnel from India and China were deployed.
- Image: Christmas Menu “No 3 and Furlough Coys, IWT , RE” Gaza Camp, Bangalore India, Christmas 1918. auctiva.com. Retrieved 16 August 2014. IWT is presumably Inland Water Transport, but it is not otherwise known to have been in India.
Historical books online
- History of the Corps of Royal Engineers Volume I by Maj-Gen Whitworth Porter 1889 Archive.org
Military History to 1860 (Note: catalogued as Volume III, but is Volume I) Archive.org
- History of the Corps of Royal Engineers Volume II by Maj-Gen Whitworth Porter 1889 Archive.org. Military History 1867- 1885, together with Part II Organization, Part III Departmental and Civil Work.
- History of the Corps of Royal Engineers, Volume III by Colonel Sir Charles M Watson. 1915. Excludes India. Covers the Sudan Campaigns and Boer War 1899-1902. Archive.org Lending Library.
- History of the Corps of Royal Engineers, Volume IV [1885-1914] by Brigadier-General W Baker Brown 1952. Archive.org Lending Library
- History of the Royal Sappers and Miners: from the formation of the Corps in March 1772, to the date when its designation was changed to that of Royal Engineers, in October 1856 by T W J Connolly, QuarterMaster of the Royal Engineers. 2nd edtion, with considerable additions 1857 (first edition 1855) With coloured plates
- Volume I, Volune II Google Books
- Same digital files HathiTrust Digital Library, where images may be rotated. Volume I, Voolume II
- Memorandum on the Employment of the Corps of Royal Engineers in India by Major G Chesney R E 1868 Google Books
- The Royal Engineer by Sir Francis B Head 1869 Google Books.
- Recollections of a Life in the British Army during the latter half of the 19th Century by Gen. Sir Richard Harrison, Royal Engineers 1908 Archive.org
- Kandahar in 1879: The Diary of Major Le Messurier R.E., Brigade Major R. E. with the Quetta Column 1880 Archive.org
- Army Equipment: Part III-Section 1 Engineers : Equipment of a Company of Engineers by Lieut-Colonel A. C. Cooke RE 1866 Google Books
- Addiscombe, its heroes and men of note by Colonel H. M. Vibart 1894 Archive.org. Addiscombe was the East India Company Military Academy in England for the training of cadets for the Engineers, Artillery and Infantry.
- Papers on subjects connected with the duties of the Corps of Royal Engineers. Volume 1 1837 to Volume 10 1849 (Quarto Series). New Series Volume 1 1851 to Volume 23 1876. The title then changed to Professional papers of the Corps of Royal Engineers Volume 1 1877 to 1905 (Volume 31?), being "Third Series". There were 2 further volumes issued in the Fourth Series the second one in 1911, for the period 1908-1911. The format then changed and individual pamphlets were issued. The following volumes are available online:
- Index to the Subjects and Authors of All Papers that Have Been Published in Royal Engineer Professional Papers from the Commencement of the Quarto Series  to the end of New Series Volume 20  published 1872 Hathi Trust Digital Library
- Professional Papers of the Corps of Royal Engineers: Index, 1837-1892 published 1893 Archive.org
- First or Quarto Series Google Books
Volume 1 1837 Volume 2 1838 Volume 3 1839 Volume 4 1840 Volume 5 1842 Volume 7 1845 Volume 8 1845 Volume 10 1849
- Note that the volumes which are digitised specifically for Archive.org may have better plans and maps compared with those that are, or are copied from, Google Books. An example is the books from the University of Toronto
- For some papers from these volumes, see 1st Afghan War, Battle of Meeanee, 1st Sikh War, 2nd China War and Abyssinian Campaign. Other papers include
- "On the fact of small fish falling during rain in India" by Captain C W Grant Bombay Engineers page 209 Volume 2 1838 Google Books
- "Memorandum of the Operations for removing the Wreck of the ' Equitable,' in the Fultah Reach of the River Hoogly" by Captain W R Fitzgerald, Bengal Engineers page 16 Volume 5 1842 Google Books
- "Madras Lighthouse. Report of Progress in the Execution of the new Machinery and illuminating Apparatus for the Madras Light" by Captain Smith. Madras Engineers page 34 Volume 5 1842. Continued on page 41 Google Books
- "Report on operations in Blowing Up Wrecks in the River Hooghly, during the years 1863-1864 and 1865" by Lieutenant W. A. J. Wallace, R.E., Officiating Executive Engineer, Strand Bank Improvement page 116 New Series Volume 16, 1868 Archive.org
- "The Frontier Railways of India" by Capt Scott-Moncrieff RE page 213 Volume 11 1885 Archive.org
- "Statistics concerning Elephants, Camels and Pack Bullocks", page 111 Volume 18, 1892 Archive.org
- "Turbines at Gokak" page 229 Volume 18, 1892 Archive.org
- "Geographical Surveying In India" by Colonel Sir T H Holdich 1898 Paper XI, Professional Papers of the Corps of Royal Engineers: Occassional Papers Volume XXIV 1898 pages 289-305 Archive.org
- The Indian Borderland, 1880-1900 by Colonel Sir T Hungerford Holdich 1901 edition, Second and cheaper edition 1909 Archive.org
- India by Colonel Sir Thomas Hungerford Holdich 1904 Archive.org
- The Gates of India, being an Historical Narrative by Colonel Sir Thomas Holdich 1910
- Political Frontiers and Boundary Making by Col. Sir Thomas H Holdich 1916
- The life and times of General Sir James Browne, R.E., K.C.B., K.C.S.I. (Buster Browne) by General J.J. McLeod Innes, RE 1905 Archive.org
- Gun-running in the Gulf and other Adventures by Brig.-Gen. H H Austin [Herbert Henry] 1926 HathiTrust Digital Library. The initial chapter Gun-running in the Gulf was of events c 1909.
- Some Rambles of a Sapper by Brigr-Genl. Herbert Henry Austin. 1928 HathiTrust Digital Library. He was posted as an Assistant Engineer to the Military Works Department in Peshawur c 1889 and was obliged to retire in 1920, as there was no longer a role for him. He spent most of his careen in India, with some years in Africa, (for the Indian Government), but appears to have remained as part of the British, not Indian, Army.
- The River of Golden Sand: being the Narrative of a Journey through China and Eastern Tibet to Burmah by Captain William Gill R. E. Volume I 1880, Volume II 1880 Condensed [memorial] edition 1883 Archive.org
- The Work of the Royal Engineers in the European War 1914-1919. Six full view editions from HathiTrust Digital Library: Water Supply - France. Part I. General development of organization, plant and works. Part II. Operations (1921); Work in the field under the engineer in chief, B. E. F.. Geological work on the Western Front (1922); Military mining (1922); Supply of engineer stores and equipment (1921); Bridging (1921); Work in the field in other theatres of war. Egypt and Palestine--Water supply (1921).
- The Signal Service in the European War of 1914-1918 (France) by R E Priestley (Late Major, R E) 1921 Archive.org. Part of the above series The Work of the Royal Engineers in the European War. Includes information about the use of carrier pigeons (Index entry)
- Mesopotamian Transport Commission. Report of the Commission appointed by the Government of India... to enquire into questions connected with the organisation and administration of the Railway and River Transport in Mesopotamia 1918. IOR/L/MIL/17/15/125/1. Qatar Digital Library. This book is also available Archive.org version mirror from Digital Library of India.
- In Kut and Captivity : with the Sixth Indian Division by Major EWC Sandes R E 1919 Archive.org
- The Military Engineer in India by Lieut.-Colonel EWC Sandes RE. Volume I 1933; Volume II 1935. Digital Repository of GIPE (Gokhale Institute of Politics and Economics [Pune India])
- The Indian Engineers, 1939-47 by Lieut.-Colonel E. W. C. Sandes 1956. Archive.org version, mirror from Digital Library of India.
- An earlier book is The Indian Sappers and Miners by E. W. C Sandes [Edward Warren Caulfeild] 1948. (726p). Covers the period from the pioneers in 1759 to the prelude to the Second World War. Available at the British Library UIN: BLL01011278725
- The Royal Engineers Museum and Library “Corps History Part 10 – Engineers of the Honourable East India Company Army 1750-1862”; Retrieved 17 Aug 2016
- michaeldr. Royal Engineers soldier abandoned in Gallipoli Great War Forum 29 June 2017. Retrieved 12 December 2018.
- idler. Book content question: R E History WW2Talk Forum 13 December 2015. Retrieved 13 December 2018.
- Corps History and Corps History CD-ROM The Institution of Royal Engineers (InstRE)
- Stuart_Bates. helmet flashes Victorian Wars Forum 15 November 2010. Retrieved 5 March 2016
- FROGSMILE. Help needed ID-ing unit flash on pith helmet Great War Forum 30 May 2011. Retrieved 13 December 2018.
- Matthew B. Walk Warily in Waziristan Great War Forum 23 April 2008. Retrieved 13 December 2018.