In the late 19th century, France embarked on an ambitious military project to build a network of 196 forts along its borders, costing nearly 679 million gold francs. The initiative was launched in 1874, following France's defeat in the Franco-Prussian War of 1870–71. The plan was overseen by General Raymond Adolphe Séré de Rivières, whose name became closely linked with the massive construction effort. The first phase of the project received 88 million francs, and by the time the project was largely complete, the cost had risen to 450 million for the forts themselves, with an additional 229 million for weapons and equipment. The development of new military technology, however, soon rendered these fortifications obsolete. In 1885, French chemist Eugène Turpin created melinite, a powerful explosive that far outperformed traditional black powder. Melinite, also known as lyddite in Britain, contained up to seven times more explosive force than black powder. This advancement had immediate and dramatic consequences for military engineering. In August 1886, the Fort de la Malmaison, a second-line fort near Laon, was used as a test site for melinite-filled shells. Over the course of several weeks, more than 170 shells were fired from 155 mm guns and 220 mm mortars, demonstrating that the stone walls of the fort could not withstand the new explosive. The results of the tests were alarming. The entire system of fortifications, including the most recently built ones such as the Fort de Douaumont, was deemed vulnerable to modern artillery. In response, engineers began to modify the forts by adding layers of special concrete and burying them deeper underground. However, these changes would not fully protect the structures from the devastating effects of World War I, where the added layers of sand and concrete actually amplified the impact of shock waves from artillery bombardments, as noted by the Museum of Engineering in Angers. The failure of traditional fortifications to keep pace with technological advancements also influenced military doctrine. By 1911, the French general staff had adopted an "offensive to the extreme" strategy, which further reduced reliance on static defenses. Despite this shift, the modernized forts still played a significant role in French military planning and were later referred to by the Germans as the "iron barrier." The story of these forts is a testament to the rapid evolution of warfare in the late 19th and early 20th centuries, where technological innovation often outpaced traditional military architecture.