A Paris paper published a statement indicating that Macmahon's army had changed the direction of its march. This statement was telegraphed to London and appeared in the papers here. It caught the attention of the then German Ambassador, who, realising its value, promptly telegraphed it to Berlin. For Moltke, of course, this was a heaven-sent opportunity of which his military genius made the fullest use. A new movement was at once set on foot, and the result was the surrender of Macmahon with his entire force. Granting that information of equal value may at any moment be obtained by a clever spy, it is obvious that commanders in the field are not only entitled, but bound to take the most drastic measures to defend themselves against spies. The work of a single spy may wreck a campaign and settle the fate of a nation, and here we have the real reason why the spy caught in the act is punished with relentless severity. "Kill that spy" is, and should be, the rule of every commander in the field. Then arises another consideration of equal importance: every commander is entitled and bound to do his utmost to secure the best possible information as to the enemy's forces, their disposition, their size, and, above all, their intentions. It is of even more importance to understand what your enemy intends to do than to know the forces which he has available to carry out his plans. How, then, are we to draw a distinction between perfectly legitimate scouting and reconnaissance work, which can involve no reprobation and no punishment, and the "spying" properly so called, which justifies the infliction of the death penalty? The answer lies in a couple of words--the spy acts under false pretences, while the soldier or scout acts quite openly; though, of course, concealing himself from observation and detection, he does not adopt any disguise or discard his uniform. The result is, that under no circumstances can a soldier wearing his uniform be treated as a spy. He may dare and do anything; if he is caught his sole punishment is that he is treated as a prisoner of war. So far as the soldier is concerned (the case of the civilian spy will be dealt with presently) disguise is the essence of spying. This point is clear beyond the possibility of misconception, and the commander who shot a soldier in uniform on the plea that he was acting as a spy would simply be committing a murder. Usually, a military spy is a soldier who has laid aside his own uniform, and either adopted civilian dress, or clothed himself in the uniform of the enemy, or a neutral, the better to escape detection. For such, there is no mercy; the penalty of detection is death. The reason is obvious: the soldier in disguise is a far more dangerous enemy than the one who openly carries out his hostile acts. In war, as in peace, the enemy in disguise is most dangerous; the false friend is the soldier's as well as the civilian's worst peril.