In 1838 the "Great Western" and the "Sirius" inaugurated the steam passenger service across the Atlantic, and the days of the liner began. By this time paddle-wheel gunboats were finding their way into the British navy, and other powers were beginning to follow the example of England. Steamships were first in action in 1840, when Sir Charles Napier employed them side by side with sailing-ships that had shared the triumphs of Nelson. This was in the attack on Acre, when England intervened to check the revolt of the Pasha of Egypt, Ibrahim, against his suzerain, the Sultan. But still the steamship was regarded as an auxiliary. The great three-decker battleships, the smart sailing frigates, were the main strength of navies. The paddle-steamer was a defective type of warship, because her paddle-boxes and paddle-wheels, and her high-placed engines, presented a huge target singularly vulnerable. A couple of shots might disable in a minute her means of propulsion. True she had masts and sails, but if she could not use her engines, the paddles would prove a drag upon all her movements. It was the invention of the screw-propeller that made steam propulsion for warships really practical. Brunel was one of the great advocates of the change. He was a man who was in many ways before his time, and he had to encounter a more than usual amount of official conservatist obstruction. For years the veteran officers who advised the Admiralty opposed and ridiculed the invention. When at last it was fitted to a gunboat, the "Rattler," it was obvious that it provided the best means of applying steam propulsion to the purposes of naval war. The propeller was safe under water, and the engines could be placed low down in the ship. By 1854, when the Crimean War began, both the British and French navies possessed a number of steam-propelled line-of-battle ships, frigates, and gunboats, fitted with the screw. They had also some old paddle-ships. But in the fleets dispatched to the Baltic and the Black Sea there were still a considerable number of sailing-ships, and a fleet still did most of its work under sail. Even the steamships had only what we should now describe as auxiliary engines. The most powerful line-of-battle ships in the British navy had engines of only 400 to 600 horsepower.[17] With such relatively small power they still had to depend chiefly on their sails. Tug-boats were attached to the fleets to tow the sailing-ships, when the steamships were using their engines. [17] Compare this with 23,000 horse-power of the "Dreadnought's" turbine engines.