Tactics and technology complement each other, and there is no better period in history for studying their interrelationship than the shift from sail to steam in the 19th century. The shell gun (raised to naval attention during the Crimean War by the Battle of Sinope, November 30, 1853) compelled navies to adopt the iron sheathing of hulls. This pointed the way to all-metal hulls (iron, then steel), which in turn both permitted and demanded as a response the installation of rifled, breech-loaded guns of major calibre. Concurrently, iron boilers and screw propellers made steam propulsion practical and gave great new freedom of maneuver. Navies were unfettered tactically from the wind, but only at the strategic price of having to remain within steaming range of coaling stations.

The sweeping consequences of these and other technological innovations lacked the crucible of war in which to test them, for it was an era of Pax Britannica, with the maritime peace kept by the Royal Navy. The Monitor and the Virginia (at the battle of Hampton Roads, March 8-9, 1862) marked the short-lived ascendancy of armour and the defense. This led to a brief revival of the ram and to some very speculative tactical concepts that looked outrageous in later days.

But the superiority of defense at sea did not last long. The tactical–technical turning point came from the observation of a few battles in East Asia around the turn of the century and from an often overlooked bit of military technology. The battles were those of the Yalu (September 17, 1894), the Yellow Sea (August 10 and 14, 1904), and Tsushima (May 27–29, 1905), in which the gun regained primacy to such an extent that the Russian vice admiral Stepan Osipovich Makarov could confidently write, “A good gun causes victory, armour only postpones defeat.” The new technology was fire control, which enabled major-calibre rounds to be placed on target at 5, then 10, and ultimately 15 miles.

By World War I the tactical issues were settled. First, big guns would dominate, a burly battleship firing a battery of them in broadside. Second, although armour could “postpone defeat,” it was all but powerless against torpedoes; therefore, a destroyer screen was essential to protect the fleet. Third, a fleet cruised in compact formation but quickly deployed in column to fight. Since the opposing fleets would close with each other at a relative 40 miles per hour, a scouting line had to be thrown out well in front to report enemy movements by wireless. Despite the elephantine appearance of a line of battleships, there would not be a moment to lose when the enemy was sighted and no margin for error.

A column of battleships was not like a column of sailing ships. With greater range and improved fire control, gunfire from most of the ships on each side could reach most of the ships on the opposite side, making concentration of firepower by a whole fleet feasible and expected. The advantage was worked out mathematically in what were called the “N-square law” and the “square law of attrition”: success would build on itself, so that any small advantage at the outset of an engagement would compound in favour of the superior force. With long-range gunnery, the advantage accrued fleet-wide, not merely ship by ship as in the days of fighting sail.

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A positional advantage could be added to this firepower advantage if the fleet “crossed the T” of the enemy, that is, if its own column crossed in front of the enemy column at a right angle and with the ships at the head of the enemy column within range of its guns. From this position at the top of the T, all the guns of the fleet could fire upon the head of the enemy column, while only the first enemy ships could return fire. This was the raking position sought by an individual sailing ship writ large, for at battleship gunnery ranges the whole force could concentrate successively on each enemy ship as it approached. It was reckoned that in fair weather and good visibility a fleet could destroy an enemy in the capped position in 20 minutes; or, if an enemy of equal strength could be surprised with unanswered fire within effective range for as little as five minutes, he would be demolished with little harm to the victor. There would be no leisurely approach, no chance to recover from a missed maneuver or a wrong turn. In fact, in practice the very swiftness of decision worked against maneuvering to cross the T. Much was made of the successful use of this tactic by the Japanese admiral Tōgō Heihachirō against the much slower Russians at Tsushima, but commanders at sea understood that the fast pace of battle worked against a T-crossing except by accident or surprise.

With one salient exception, there were no unforeseen tactics in World War I. The exception was the ease with which a fleet could be surprised at sea. The Battle of Jutland (May 31, 1916) was fought in great confusion, owing to a fog of smoke from the stacks and guns of 250 ships as well as the sloppy work of the commanders of the two scouting forces. The German commander, Reinhard Scheer, twice had his T capped for lack of visibility; for the same reason, the British commander, Sir John Jellicoe, twice was unable to exploit this, the ideal tactical position.

The lesser engagements of the war were also marked by surprise, but from another source. At one time or another, both the Germans and British broke each other’s codes. Special intelligence and attempts to entrap a weaker enemy were rife throughout the war, leading to surprise in each of the battles in the North Sea: Helgoland Bight (August 28, 1914), Dogger Bank (January 24, 1915), and Jutland itself.