And, just as they reached the somewhat sheltering woods, there sounded from the air above them several explosions, and with them was an undercurrent of humming and droning as if from a million swarms of bees.

“The Boche aeroplanes!  They’re right over us—­a whole flock of ’em!” cried Roger.  “And they’re dropping bombs on us!”

CHAPTER XVII

A BATTLE OF THE AIR

What Roger had said was only too true.  The advance of the American army had been halted, at least temporarily, by a sudden attack from a large number of German aeroplanes.  The Fokkers had arisen from far enough back of the place where the American shells were falling to escape them.  And then they had sailed directly over the advancing Americans, the center formation of the Huns’ ships of the air being almost directly over where our five heroes were now stationed in the woods.

“Bombs!  I should say so!” cried Jimmy, as one landed on the other edge of the woods, and blew a great hole in the ground.  “This is getting too close for comfort!”

The German machines, having flown from the direction of their own lines across the American front, dropping bombs that did great execution, were now coming back again, to repeat the performance, it was very evident.

“Why didn’t we bring up some anti-aircraft guns?” demanded Bob, as though some officer, immediately over him, had neglected this precaution.

“Guess no one expected the Huns would try this trick,” said Roger.  “It’s a daring move, all right.”

“And it’s a dangerous one for us, too!” added Jimmy, grimly.  “These woods are a pretty good protection against shrapnel and machine-gun fire, but they’re absolutely useless when it comes to screening us from aeroplane bombs.  Of course we can hide from the sight of the flying Huns, but they must know this wood is full of Americans, and a bomb dropped anywhere among the trees will get some of us.  It’s fierce!”

“You said it!” cried Franz.  “Wow!  That was a bad one!”

A bomb—­one of the winged affairs that wrought such deadly havoc in Paris and London—­had fallen not one hundred feet from where the five Brothers were crouching in the underbrush.  The concussion jarred them, and the force of the explosion uprooted several large trees that injured a number of the command, while the bomb itself killed three in dreadful fashion.

“Why don’t our flying lads get after ’em?” demanded Franz.  “Surely we have some planes over here now—­in fact, I know we have; though not nearly enough.  Where are they?”

Well might he ask that, for the Germans were circling around, now over the woods and again over the open country, dropping their bombs, which exploded, doing terrible damage, killing and wounding many.

Suddenly Bob, who was gazing skyward in despair, clutched Jimmy’s arm and cried: 

“Look!  Look!  There they are!  There come our boys!  American machines!  See the Indian head!  Now we’ll see Mr. Hun on the run!  Oh, boy!”