More permanent fortifications were built during the first half of the 19th century in response to feared foreign attacks with new threats to the British empire, including Napoleon's French troops in 1810, and the Russian Pacific Fleet in the 1850s (during the Crimean War).
During the early part of the 19th century, more enduring fortifications were constructed in response to anticipated foreign attacks, such as Napoleon's French forces in 1810 and the Russian Pacific Fleet in the 1850s (during the Crimean War).