Repairs were made during the Revolutionary and Napoleonic Wars with France, and the castle was modernised to enable it to hold 24-pounder (10.8 kg) guns. Fresh fears of invasion followed in the 1850s, leading to heavier, 32-pounder (14.5 kg) armament being installed and new gun batteries being laid out on both sides of the castle. Technological developments rapidly made these defences obsolete, however, and a fresh phase of work between 1861 and 1874 created sixty-one gun positions in two long, granite-faced batteries alongside the older castle. These held very heavy weapons, including massive 12.5 inch, 38 ton (317 mm, 39,000 kg) rifled muzzle-loading guns. As the century progressed, these too became outdated and lighter, quick-firing guns were installed at the castle to replace them.