Short answers, pulled from the story.
Railways have been employed for military purposes since the Revolutions of 1848. Prussia's VI Corps, about 12,000 men, was transported by rail to Kraków in 1846, and Prussian forces used railways during the First Schleswig War in 1849-1851.
The Grand Crimean Central Railway was a purpose-built military railway 7 miles long, constructed during the severe winter of 1855 to supply British Army troops besieging Sevastopol from Balaklava during the Crimean War.
The Death Railway is the common name for the Burma-Siam Railway, built by Japan during World War II. It earned the name because of the large numbers of Allied prisoners-of-war and Asian labourers who died during its construction.
The Peacekeeper Rail Garrison was a mobile intercontinental ballistic missile system developed by the US Air Force in the 1980s, designed to be moved continuously around the American rail network. It never reached operational status.
The early phase of World War I was shaped significantly by railway-based mobilization. Germany's Schlieffen Plan relied on strategic railways to defeat France before Russia could mobilize, but Russia mobilized faster than anticipated, causing the plan to fail and the Western Front to stall into trench warfare.
Railways played an important role in the logistics of the 2022 Russian invasion of Ukraine. They served as a key means of supplying and sustaining operations across a large front, continuing a role railways have filled in major conflicts since the nineteenth century.