Richard Rhodes’s most recent book is “Hell and Good Company: The Spanish Civil War and the World It Made.”

Six Weeks in World War I That Forever Changed the Nature of Warfare

By Diana Preston

Bloomsbury. 340 pp. $28

The phrase “weapons of mass destruction” has a recent ring. We might imagine it was coined in the George W. Bush era to refer to Saddam Hussein’s nonexistent nuclear arsenal, or in the 1960s, when the United States and the Soviet Union first deployed long-range nuclear missiles. British historian Diana Preston’s thorough research teaches us otherwise: The archbishop of Canterbury coined the phrase in 1937, she reports, to characterize the German bombing of Guernica during the Spanish Civil War, while the weapons of mass destruction themselves originated during World War I.

Missiles were not among them; the long-range rocket was developed during World War II. The WMD Preston exhumes are poison gas, submarines and aerial bombardment, the latter two deliberately targeted on civilians as well as combatants. Germany originated all three, part of a policy of schrecklichkeit, or terror, that shocked a world still clinging to the 18th-century conviction that wars should be fought only between armies on the battlefield and civilians should be spared — a conviction sealed with solemn treaties among the European powers. Germany insisted instead that a nation fighting for its life had an inherent right to use every means at hand to defend itself. Its scientists, engineers and military leaders argued as well that the new methods of mass killing (a) were no worse than high explosives and (b) might shorten the war and thus save lives. Such rationales proved small comfort to those who died choking on chlorine gas, drowning in the churn of their torpedoed luxury liner or burning in the inferno of a zeppelin-delivered fall of firebombs.

”A Higher Form of Killing: Six Weeks in World War I That Forever Changed The Nature of Warfare” by Diana Preston (Bloomsbury)

All three forms of WMD emerged early in the war, once the stall of trench warfare took hold and the front lines froze. German technicians first released greenish chlorine gas out of high-pressure canisters at Ypres, Belgium, on April 22, 1915, to flow with the spring breeze into French and Canadian trenches to clear the way for a German breakthrough. Without gas masks, which had yet to be developed, the victims suffered terribly, but the cautious Germans hesitated to press their advantage, and no breakthrough followed. In the months and years to come, masks were improvised and then manufactured; one side or the other introduced 63 kinds of poison gases and used them in various deadly combinations. But the 450-mile line of opposing trenches remained stalemated until the newly invented tank and U.S. entry into the war allowed the Allies to overwhelm the German defense.

The submarine and aerial bombardment were both German responses to the increasingly effective Allied naval blockade that was starving the German population and choking off the supply of war materiel. Germany suspected, rightly, that the British were secretly transporting munitions from the supposedly neutral United States in civilian freighters and even passenger vessels, which were officially off-limits. With their new diesel submarines — a naval technology the British Admiralty had scorned — the Germans began torpedoing such shipping without warning, most notoriously the passenger liner Lusitania, sunk on May 7, 1915, with the loss of 1,198 lives, including 128 Americans. That success may have cost them the war: “Remember the Lusitania” served as a slogan on recruitment posters when the United States entered the conflict in 1917 after further sinkings and the exposure of a secret German offer to Mexico to help it reconquer Texas, New Mexico and Arizona if it joined Germany in the fight.

German zeppelins — rigid, cigar-shaped dirigibles up to 536 feet long, lofted with hydrogen gas and capable of carrying 4,400 pounds of bombs — began bombing England in January 1915. The kaiser, who was Queen Victoria’s eldest grandson, forbade them to bomb London but changed his mind in May, asking only that they avoid hitting historic buildings. Zeppelins raided England more than 50 times between 1915 and 1917, by which time the British had devised a combination of explosive and incendiary shells for fighter aircraft that effectively ended the menace by igniting the hydrogen cells and burning the huge craft out of the sky. German Gotha and Giant bombers then replaced the zeppelins for the last year of the war, causing almost equal destruction across a much shorter span of time.

The German program of firebombing never succeeded in creating the mass fires it intended. The most lethal German firebomb, the two-pound thermite and magnesium Elektron, developed only at the end of the war and never deployed, saw full service in Spain, most notoriously in the firebombing of Guernica, when thousands of Elektrons mixed with high explosives burned down that ancient Basque capital to extensive loss of life. Firebombing came back to haunt Germany during World War II with the Allied incendiary attacks on Hamburg and Dresden, the latter resulting in more deaths than those in either Hiroshima or Nagasaki.

Preston, whose previous books include a history of the sinking of the Lusitania, tells this grim story well. Her extensive archival research fills in the historical chronology with well-selected quotations from personal accounts of participants at every level of civilian and military life and of government. I would like to have seen more discussion of German military theorizing about the value of the new weapons — Preston makes it seem as if the fundamental justification was indeed schrecklichkeit, if not simply the kaiser’s perpetual, dyspeptic indignation — but perhaps the German military gave little thought to long-term strategy in the face of the colossal loss of life on all sides: 10 million military deaths, 7 million civilians, total casualties of more than 37 million across that first world-scale war.

She observes that poison gas was the first successful deterrent, noting its nonuse during World War II, but she is counting only combatants. The German institute that developed poison gases for the Great War also developed an insecticide, Zyklon-A, which in a later form, Zyklon-B, poisoned more than two-thirds of the 6 million Jews murdered in the Holocaust.

Perhaps ironically, the first weapons of mass destruction that truly deserve the designation — the atomic and hydrogen bombs — have proved to be universally deterrent. Fifteen million people died in 1943, more than in any other year in the history of war and the high mark on an exponential march of man-made death stretching back to the 18th century. But beginning in 1945, man-made deaths annually dropped to about 1 million to 2 million per year and have remained at that level ever since — nothing to be proud of, to be sure, but far fewer deaths annually than result from smoking. The price of nuclear deterrence, of course, has been a sword of Damocles hanging over our heads: mass death on an unprecedented scale in the form of nuclear winter. Near the end of this gripping and excellent book, Preston quotes Albert Einstein commenting, “It has become appallingly obvious that our technology has exceeded our humanity.” It would be more accurate to say that our technology has exceeded our inhumanity: We are all purveyors of schrecklichkeit now.