During the two main naval engagements of the Russo-Japanese War, fire control played a relatively small part. During the Battle of the Yellow Sea on the 10th August 1905, most of the firing occurred after the Russian fleet avoided the Japanese attempt to 'cross the T' of their line. The Russians turned onto a parallel course to that of the Japanese fleet. With both fleets steaming at a similar speed and making no attempt to manoeuvre, fire control solutions were relatively straightforward. Tsushima proceeded similarly, with the Japanese only opening fire once they were on a parallel course to the Russians. More significant in the Japanese victory at sea were other factors. Aggressive use of lighter forces brought significant rewards. The destroyer raid on the Russian base at Port Arthur heavily damaged two battleships and a cruiser for little cost. Minelaying outside the base sank the battleship Petropavlovsk and heavily damaged the Pobeda. Most of the Russian Pacific Fleet would be sunk at anchor in Port Arthur, blockaded in by the IJN and under fire from shore batteries of the Japanese Army. Rozhestvensky's 2nd Pacific Squadron, defeated by Togo at Tsushima, was a poorly trained force, with his sailors unable to train during the trip. Its ships had been worn out by the long passage from St Petersburg - the combined effects of fouling and undermaintained boilers meant that Rozhestvensky's ships were 3 knots slower than their design speed. Rozhestvensky also prevented his fleet from using radio, afraid that the Japanese might use it to track his position; the Japanese made liberal use of it, especially amongst their scouting ships. This meant that Togo was always aware of Rozhestvensky's position, allowing him to move into a superior position.

During the Russo-Japanese War, and, more generally, naval fire control was going through something of a revolution. Older methods of aiming by little more than guesswork were being replaced by a complicated system of rangefinders, early mechanical computers and electrical and hydraulic systems. The first step in this chain was the introduction of rangefinders. These allowed the ship's gunnery officers to get an accurate range to the target, a key part of gunlaying. There had been early experiments in rangefinding as early as 1855, though none found any success. The first truly successful rangefinder was developed by Archibald Barr and William Stroud in 1888. They founded a company to produce and market their designs, which saw an early success when one won a Royal Navy trial in 1893. Their rangefinders saw significant commercial success, with the company selling over 150 units by March 1898, including to the Japanese. Rangefinders saw considerable improvements in accuracy and range over the early years of the 20th Century. The first Barr & Stroud instruments were accurate out to 3,000 yards, while their FA3 model of 1903 could reach out to 8,000.

Another important step was the innovation of 'continuous aim'. Developed by the Royal Navy's Percy Scott in 1898, it was a method of removing the effect of roll from guns laid by hand. Earlier gunners had laid their guns at a fixed elevation, and waited until the target crossed their sight as the ship rolled. This was difficult to do, especially at long range, as the target might only appear in the sight for a brief instant. Under continuous aim, the gun was continually elevated and depressed so that the sight was kept on the target. This cancelled out the effects of the roll, and led to a great increase in accuracy. In 1899, Scott's cruiser Scylla would score 80% accuracy in the RN's gunlaying test, twice the usual high score of 40%. While continuous aim was highly effective, it could only be done with lighter guns. Heavier guns required large electric or hydraulic systems to use it, or had to use less efficient methods of fire control. Scott was also an early adopter of telescopic sights, though the RN had sought guidance on the topic shortly before his first use of them.

Initially, ranges had to be transferred from the rangefinders to the guns by voice-pipes, a slow and relatively inaccurate method. In 1894, Barr & Stroud began work on electrical instruments to do this. They found their first customer in the IJN in 1898, with the RN following a year later. These used electrical motors to turn dials at the guns to conform with the ranges set by the rangefinder operators. The first instruments were clumsy and inaccurate, but they soon improved, especially as Barr & Stroud began to encounter foreign competition. In 1902, Lieutenant John Dumaresq invented the first 'fire control computer'. The eponymous device used a system of sliding bars and cams to plot the course and speed of the user's ship and their target. The deflection (the amount by which the target had to be lead) and the range-rate (the rate at which the range was changing) could be read off. The Dumaresq was trialled aboard Dumaresq's ship, the Victorious, before winning an RN competition in 1904. It was brought to the market by Elliott Bros in August 1904, with several devices being sold to the RN. Meanwhile, Percy Scott was working with Vickers to design a 'Range Clock'. This was a device which kept a constant record of the range. Rangefinders could not constantly take the range, so the Range Clock would provide an interpolation between individual measurements. As originally designed, the hands of the clock rotated at a rate set by the user following multiple observations of the target's range, but when combined with the Dumaresq (which gave the range rate directly), it proved highly useful. The first Vickers clocks were available in 1905, and a full order of 246 had been produced by the end of 1906.