Italy entered the second world war in much the same circumstances as it entered the first. It waited nine months to see which side was likely to win and then joined it in the hope of sharing the spoils. The only difference was that in 1940 Mussolini failed to identify the winner.

Italy in 1915 was still a member of the Triple Alliance with Germany and Austria. But feelings of “sacred egoism”, which its prime minister regarded as the determinant of foreign policy, persuaded it to attack its long-standing allies. The egoism had to be nourished by seizing the Italian-speaking areas of the Habsburg Empire, principally the Trentino and the city of Trieste. But it also demanded the German-speaking south Tyrol as well as Istria, Albania and parts of Dalmatia. Self-determination, Italians argued after the war, was all very well for other parts of the world but was inappropriate for the Adriatic.

The price of egoism was 689,000 dead Italian soldiers (excluding civilians and the Austrian casualties), many of them southern peasants who could not have cared less whether Trieste or the Trentino became part of Italy. “Sacred egoism” was a hangover from the Risorgimento, a concern of mainly urban, northern, middle-class young men who argued that Italy, hitherto a weak and unsatisfactory state, would feel itself “redeemed” by the conquest of these territories. Only then would their nation be treated seriously by the Great Powers.

Many books have described Italy's second world war, recounting how the British and American armies spent 22 months slogging their way from one end of the country to another, but its predecessor has been largely neglected. Mark Thompson's The White War, an excellent narrative history, remedies this deficiency in well-judged, well-written prose. The author comes to his subject from a useful and unusual angle - he has previously written about the Balkans - and he displays an impressive acquaintance with the background and the terrain. The battlefields have evidently been well tramped.

Times Archive, 1915: Spirit of Italian soldiers

'No fear is felt or shown of Lady Death. We all want to be heroes if possible'

• The Sword of Italy

• The Austrian Attack

Background

• Extract: The White War

The tale itself is a tragic and relentless one. It is bad enough to have three battles of Ypres on the Western Front, but the Italians and the Austrians fought no fewer than 12 battles of the Isonzo, a statistic that by itself testifies to the failure of imagination of General Cadorna,the Italian commander-in-chief. All ended more or less in stalemate, the front line advancing or retreating a few kilometres, except the last (usually known as Caporetto), which was an Austrian-German victory and proof of Cadorna's incompetence. Italy's subsequent triumph at Vittorio Veneto, much trumpeted at the time and commemorated in street-names since, was a victory achieved only with French and British support at a time when Austria was already seeking an armistice.

Fortunately, the author spares us 12 consecutive chapters on the Isonzo by interspersing his account of the action with perceptive reflections and useful analyses of subjects such as the history of Trieste, the mood in Vienna, the servility of Italian newspapers, the irresponsibility of the Italian government, and the poetry - sometimes brutal and sometimes lyrical - of the Italian war poets.

Thompson sympathetically records the tribulations of Italian soldiers, the worst fed, worst led, worst paid, worst clad and worst equipped among the western powers; they were expected to cut through Austrian barbed wire with implements resembling garden secateurs. Of those that were captured, many died of hunger, for they were the only prisoners in Europe who were not sent food parcels: their government feared such a policy might be an incentive to surrender.

They were also punished more savagely than their counterparts in the armies of Germany, France, Austria and Britain. Cadorna insisted that even mildly mutinous behaviour should be countered with summary executions. He also revived the ancient Roman custom of decimation, executing by lot a proportion of a censured unit's soldiers, a practice guaranteed to kill innocent men. Before offensives, military police with machine guns were stationed behind the trenches, ready to shoot at soldiers who appeared to dawdle as they were going over the top.

There are many bunglers in Thompson's book, mainly senior officers and government ministers, but Cadorna is justly identified as the most obnoxious. How he managed to browbeat the cabinet and keep his job for so long remains a mystery; he might even have survived the disaster of Caporetto had Lloyd George and the French not insisted on his departure.

Cadorna was as unimaginative as General Haig and as tactically obtuse. He failed to concentrate his forces, he attacked on too wide a front, he sent his men over open ground against barbed wire and machine guns, and he repeated his mistakes. He invariably outnumbered the Austrians, who were fighting on two other fronts, by a ratio of five to two, and he almost always suffered higher casualties than his opponents. His reaction to setbacks for which he was responsible was to sack or transfer his officers, particularly those who showed spirit, imagination and independence: during the two and a half years of his command he removed more than 200 generals and more than 600 colonels and battalion commanders. And when things went really wrong, this deluded and complacent man consoled himself with the belief that not even Napoleon would have achieved more had he also been fighting on the Isonzo.

The White War by Mark Thompson
Faber £25 pp454

Times Recommends

• The Sisters Who Would Be Queen by Leanda de Lisle
• The TS Eliot prize preview
• It Still Moves: Lost Songs, Lost Highways and the Search for the next American Music by Amanda Petrusich