An elementary guide to Afghanistan and Baker St

We all know that the British and American military authorities do not allow much news to leak out about what is happening in Afghanistan, but it is enough to read closely. For example, the case I will now tell you about occurred long before the war moved to the vicinity of Kandahar.

The person whose story I'm going to relate enrolled as a medical officer in the English deployment in Afghanistan. He registered in that very selective group known as the Fifth Northumberland Fusiliers, but, as it happens, he was transferred to the Royal Berkshires. As part of that outfit, he found himself facing Afghan fighters to the north-west of Kandahar, more or less near Mundabad. That's where an error in "intelligence" occurred.

The English were told that there were fewer Afghans than was the case and that they were more poorly armed. The English went on the attack and they were massacred - at least 40% died - at the mountain pass called Khusk-i-Nakhud. The country's mountain passes are terrible and, as journalists have reported, the Afghans are not accustomed to taking prisoners. Our friend was hit in the shoulder by a bullet from one of those deadly - if antiquated - Jezail muskets. The bullet cracked the bone and cut off the subclavian artery, and our hero was barely saved by a brave orderly.

He returned to London to recuperate, and a little episode lets him know how much the memory of that tragic battle was in everyone's mind. When he meets the person with whom he is going to share an apartment, the roommate says to him, "From what I can tell, you were in Afghanistan."

Asked later to explain how he knew that, the person says he thought to himself: "This man has something medical and something military about him. He's been in a tropical climate, because he has a very dark face, but that is not his natural colouring, because his wrists are pale. He has suffered hardships and illnesses, as his emaciated face demonstrates. In addition, he was wounded in his left arm. He keeps the arm in a rigid and not very natural position.

"In which tropical country could a doctor in the British army have been forced to put up with difficult exertion and hardships? In Afghanistan, of course."

This conversation took place in Baker Street. The medic was Dr Watson. His interlocutor was Sherlock Holmes. Watson was wounded in what at the time was known as the battle of Maiwand, on July 27, 1880. In London, the newspaper The Graphic reported it on August 7 (news reports were delayed back then). We know about it from the early chapters of A Study In Scarlet.

The experience marked Watson for ever. In the story The Boscombe Valley Mystery, he says his experience in Afghanistan made him forever a prepared and inexhaustible traveller. But when, in The Sign Of Four, Holmes offers him some cocaine, Watson says that after his duty in Afghanistan, his body cannot handle new experiences. Shortly afterwards, he says he likes to stay seated and take care of his wounded arm, which suffers with each change in temperature. In The Musgrave Ritual, Watson reflects on the ways in which the Afghan campaign left deep marks on him.

In fact, Watson always loved to talk about his time in Afghanistan, but people usually wouldn't listen. With much effort (in The Reigate Squires), he persuades Holmes to visit a fellow soldier, Colonel Hayter. In The Naval Treaty, he tries in vain to interest a certain Phelps - a peevish and nervous person - in his Afghan adventures. In The Sign of Four, he busies himself trying to tell war stories to Miss Morstan, and manages to pique her interest only once.

Veterans, especially if wounded, are boring. But the memory of Afghanistan is always present. In The Adventure Of The Empty House, while talking about Holmes's arch enemy, Moriarty, he comes upon the file of a Colonel Moran, "the second-most dangerous man in London", who served in Kabul. Echoes of the Afghan war return in The Crooked Man.

Finally, in both The Adventure Of The Cardboard Box and in The Resident Patient, Holmes pulls off a masterstroke of what he erroneously calls "deduction". While they are seated, relaxing in their apartment, Holmes suddenly comments on war without prompting: "You are right Watson. It does seem to me to be the most ridiculous way to resolve a dispute."

Watson agrees, but then he asks how Holmes knew what he was thinking. The explanation: by following the simple movement of Watson's eyes to the various parts of the room, Holmes was able to reconstruct precisely Watson's train of thought. And then, realising that his friend was thinking about various and terrible wartime episodes, and seeing that his friend touched the old wound, Holmes inferred that he was dejectedly thinking about how war is the most absurd way to settle international disputes. Elementary, my dear Watson.

Umberto Eco, L'Espresso 2002, from The Guardian