Many years ago, I found an interesting series of intelligence reports in the files of Sir Douglas Haig, the British commander in the First World War. General Haig was interested in the condition of the German soldiers, so his intelligence officer provided him with a running commentary on the composition of the sausages fed to German troops. According to Haig's logic, a time would come when the sausage would become inedible (due to the shortage of meat), and the morale of German troops would consequently collapse.
I suspect John Keegan would appreciate that bit of evidence, if he doesn't already know about it. Keegan is a meat-and-potatoes kind of military historian: He adores soldiers and is entranced by war. But he's suspicious of those who operate on the periphery of war - the spies, agents provocateurs, and James Bond types. He feels they're often morally suspect and that their actual contribution to military victory has too often been exaggerated.
"War is ultimately about doing, not thinking," Keegan argues. "Only force finally counts." With "Intelligence in War," he presents a series of case studies, including Nelson's pursuit of the Napoleonic fleet, Stonewall Jackson's Shenandoah campaign, the naval battles of the Great War, and three campaigns from World War II.
According to Keegan, each of these case studies demonstrates that, whether good or bad, intelligence seldom has a profound effect upon the outcome of a battle.
The Battle of Midway illustrates his point rather well. It took place because of an intelligence coup on the part of the Americans. A combination of interception, decoding, and informed speculation convinced them that the Japanese, in early June 1942, would not strike westward into the Indian Ocean or southward toward Australia, but instead eastward toward Midway, the last American outpost in the vicinity. A surprise attack on the approaching Japanese fleet was therefore planned.
What followed was perhaps the greatest naval victory in history. Success, however, resulted not from good intelligence but a series of fortuitous circumstances. The Japanese managed to destroy the first five squadrons launched from American carriers.
The sixth squadron, consisting of dive-bombers, initially got lost, but then found the Japanese fleet by accident, and at a particularly opportune time. Three of four Japanese carriers were subsequently destroyed in just five minutes.
In other words, while the battle itself resulted because of good intelligence, its outcome had nothing to do with cloaks and daggers. In fact, intelligence brought into being a battle which could so easily have been a great American defeat.
Keegan recognizes that intelligence is essential to every military operation, but he objects to the way our prolific spy novelists have given the impression that wars hinge on the exploits of one or two shadowy figures.
Intelligence is designed to penetrate the fog of war, which it occasionally does. But a clearer picture of enemy intentions does not lead resolutely to military victory - battles still have to be won with blood and brawn. And, quite frequently, intelligence renders the fog of war even more opaque, as was the case with Haig and his inedible sausages, which suggested that the Germans would be beaten long before they actually were.
Sir John Keegan is a British national treasure. I sometimes wonder if perhaps he has been cloned and that there are in fact two or three Keegans working side by side at their own computers. In the past year, he has published three books, in addition to innumerable articles. That kind of productivity often comes at a cost - prose becomes sloppy and research incomplete. But it's difficult to fault any of Keegan's recent work. His analysis is as sharp as ever, and it's all written with his characteristic flair.
Espionage would seem more important than ever as we pursue elusive terrorists, but the limitations of intelligence have never been so rudely exposed as in recent years. The spooks failed to warn us about 9/11, they failed to determine whether Saddam Hussein had weapons of mass destruction, and they have failed to locate Osama bin Laden. Our present plight demonstrates Keegan's central point: Wars are won by soldiers, not by shifty men with decoder rings.
• Gerard DeGroot is a professor of modern history at the University of St. Andrews in Scotland.