Protracted siege warfare and mining did not, however, play a major part in the Franco-Prussian War of 1870-71, during which the French fortresses were forced to surrender through containment or powerful bombardment. After 1870, the opinion of most artillery and engineer officers in the great military powers was that long-range, large-calibre artillery, especially mortars and howitzers with plunging fire, would always defeat fortresses that previously could be breached only by mining.⁵

By the 1880s it seemed that fortresses had become obsolete, along with the ancient means of assaulting them. There were, however, opposing trends. The Russo-Turkish War had involved a five-month siege of Pleva in 1877, conducted by Todleben. During the American Civil War mining was used against field works rather than a fortress at the siege of Petersburg. A 511ft gallery was driven by the 48th Pennsylvania Infantry, which was both commanded by and composed mainly of coal miners. The unit laid a charge of 3,600kg at 6m depth beneath a Confederate earthwork known as Elliott’s Salient, which was blown on 30 July 1864. The mine killed 250 to 350 Confederate soldiers, but in the resulting Battle of the Crater the Union attack was badly coordinated and many of the attackers were trapped in the crater by a counterattack.⁶

There was an unexpected revival of mine warfare during the Russo-Japanese War of 1904-05, especially during the siege by the Japanese of Port Arthur. The position was defended by a ring of concrete forts linked by strong points and entrenchments but, possibly believing that the ground was too hard for mining, the Russians failed to construct an adequate system of countermines. They also lacked tools and only began mining after the Japanese underground attacks had started. By the standards of the Crimean War the mining was unsophisticated and the lack of training of the Russians, who were to suffer defeat, demonstrated that skills could very quickly be lost. The first contact underground demonstrates the Russian lack of skill. A shallow Russian countermine at Fort II caved in beneath a shell crater and the tunnel was deepened with a shaft sunk to 4m. From the bottom of the shaft the Russians began a gallery inclined downwards and, on 20 October 1904, they heard noises of Japanese mining. On 26th, after determining the direction of the Japanese attack by listening, the Russians loaded the end of the gallery with 123kg of gunpowder, continuing picking until the last moment to deceive the Japanese. They blew the following day, destroying the Japanese gallery and killing several miners. However, they had miscalculated the weight of the charge, which was probably intended only as a camouflet, and broke surface to form a crater, as well as bringing down part of their own defences and effectively loosening the ground, facilitating the Japanese advance.

By December 1904 charges of 900kg to 1,300kg were used, and on 31 December the Japanese blew 5,000kg of dynamite.⁷ High explosives, such as TNT and dynamite, invented in the 1860s, were at least twice as powerful as gunpowder, but did not immediately replace it in mining owing to their high rate of detonation. The war also saw the construction of very strong field fortifications, involving earthworks, entrenchments and barbed wire, which were so resistant to attack that mining was also used against them. In the winter of 1904-05, when the opponents were facing one another on the banks of the Shaho river 100m apart, the Russians advanced by sapping and mining to capture the Japanese bridgehead. They also attempted this at the village of Li-chia-pu, where the positions were about 300m apart. In the final land action of the war, for three weeks in February to March 1905 until the Russians were forced to fall back, armies of over 300,000 on each side faced each other from entrenchments at Mukden on a forty-mile front.⁸