That which France had been unable to suppose even Germany capable of, happened:  The treaty with Belgium became a scrap of paper and the main attack upon France was made by way of the north.

But the expectation that Nancy would be one of the first objectives of the Hun-rampant was not without fulfillment.  For the hordes advanced in five armies; and the fifth, the German left wing under Crown Prince Rupprecht of Bavaria, was ordered to swarm into France south of that of the Imperial Crown Prince, spread itself across country behind the French armies facing northward, join with Von Kluck’s right wing somewhere west of Paris, and “bag” the French—­armies, capital and all—­“on or about” September 1.

It was all perfectly practicable—­on paper.  The only difficulty was that there were so many things the German staff had omitted from its careful calculations—­omitted, perforce, because it had never guessed their existence.  And that spoiled their reckoning.

Foch had, for years, been teaching that fighting demands supreme flexibility, adaptability; that war is full of surprises which must be met as they arise; that morale, the spiritual force of an army, is subject to fluctuations caused by dozens of conditions which cannot be foreseen and must be overcome.  The phrase oftenest on his lips was:  “What have we to do here?” For, as he conceived warfare, officers and even privates must constantly be asking themselves that.  One plan goes awry.  Very well! we’ll find a better.

But Foch had not trained the German general staff.  They made war otherwise.  And well he knew it!  Well he knew what happened to them when their “blue prints” would not fit unexpected conditions.

He knew that they expected to take Nancy easily, that they were looking for some effort to defend it, but not for a French attack.

They did not know his maxim:  “The best means of defense is to attack.”

He attacked.  His Twentieth corps fought its way through the center of the Bavarian army, into German Lorraine.  Then something happened.  Just what it was is not clear—­but doubtless will be some day.  The offensive had to be abandoned and the French troops had to withdraw from German soil to defend their own.

How bitter was the disappointment to Foch we may guess but shall never know.  But remaking plans in his genius.

“What have we to do here?” he asked himself.

Then, “in the twinkling of an eye,” says one military historian, “General Foch found the solution to the defense problem wherewith he was so suddenly confronted when his offensive failed of support.”

XIII

THE BATTLE OF LORRAINE

What is known as the battle of Lorraine began at the declaration of war and lasted till August 26—­though the major part of it was fought in the last six of those days.

I shall not go into details about it here, except to recall that it was in this fighting that General Castelnau lost his oldest son, stricken almost at the father’s side.