The title of the book is taken from the Duke of Wellington who always stressed the importance of knowing what your enemy is up to.
The writer is the distinguished military historian and strategist Basil Liddell Hart, who advocated fast-moving armoured divisions striking quickly and deeply into the enemy.
This was the philosophy behind the Blitzkrieg and the swift overrunning of Western Europe by the Nazis.
Liddell Hart based his account on interviews he conducted with German field marshals.
One question which was resolved was why the Wehrmacht let the British Expeditionary Force off the hook in escaping via Dunkirk.
The explanation is that Hitler, who always had a great respect for the British Empire, genuinely believed that the United Kingdom would parlay peace terms.
The two Edwards – the king who abdicated and Lord Halifax – would have made for two appeasing and sympathetic heads of state and Joe Kennedy (another appeaser) had been installed as US Ambassador to the UK.
Given the choice between Bolshevism and losing their land – and retaining it by accepting Nazism – most of the aristocratic class should have opted for the latter.
The second question which the generals interviewed answered is why and how the Wehrmacht fought so impressively in the Western Europe after the Normandy landings.
There was the oath to Hitler as supreme commander and embarrassment as the soldiers in the East were combating the Red Army.
Other factors not mentioned were the development of the V2 rocket, to which the Allies had no defence, and some tactical failures by the Allies such as Arnhem.
Hitler’s final gamble was a second thrust through the Ardennes.
This did catch the American forces unawares but – once the fog had cleared – the Allied air supremacy and lack of gasoline proved fatal and the thrust stopped a long way short of the coast.
Gasoline shortage emphasised one problem for the Liddell Hart philosophy, namely supply.
Rommel’s Afrika Korps were so deep into North Africa that they were far ahead of their supply routes and the same problem was experienced in the Caucasus.
Another major problem was Hitler’s insistence on standing one’s ground when the alternative of an organised retreat was the only sound military option.
A minor criticism of the book is its editing.
The first section is on the German generals who adopted his philosophy, notably Erwin Rommel and Hans Guderuan, but their successes are later repeated in the chronological account of the war.
Otherwise I found this book illuminating and instructive.