"Now then, give it to them!" cried Bert, and let fly his first snowball, which landed on the top of the fort's wall. Soon the air was full of snowballs, flying one way and another. Many failed to do any damage, but some went true, and soon Bert received a snowball full in the breast and another in the shoulder. Then he slipped and fell and his own snowballs were lost. The attacking party got to within fifty feet of the fort, but then the ammunition gave out and they were forced to retreat, which they did in quick order. "Hurrah! they can't take the fort!" cried those inside of the stronghold, and blew their horns more wildly than ever. But their own ammunition was low and they made other snowballs as quickly as they could, using the pile of snow in the middle of the fort for that purpose. Back of the barn the attacking party held a consultation. "I've got a plan," said a boy named Ned Brown. "Let us divide into two parties and one move on the fort from the front and the other from the back. Then, if they attack one party, the other party can sneak in and climb over the fort wall and capture the flag." "All right, let us do that," said Bert. Waiting until each boy had a dozen or more snowballs, half of the attacking force moved away along a fence until the rear of the fort was gained. Then, with another cheer, all set out for the fort. It was a grand rush and soon the air was once more filled with snowballs, much to the delight of the spectators, who began to cheer both sides. "Oh, I hope they get into the fort this time," said Nan. "I hope they don't," answered another girl, who had a brother in the fort. Inside the fort the boys were having rather a hard time of it. They were close together, and a snowball coming over the walls was almost certain to hit one or another. More than this, the pile of snow around the flag was growing small, so that the flag was in great danger of toppling over. Up the two sides of the hill came the invaders, Bert leading the detachment that was to attack the rear. He was hit again, but did not falter, and a moment later found himself at the very wall. "Get back there!" roared a boy from the fort and threw a large lump of soft snow directly into his face. But Bert threw the lump back and the boy slipped and fell flat. Then, amid a perfect shower of snowballs, Bert and two other boys fairly tumbled into the fort. "Defend the flag! Defend the flag!" was the rallying cry of the fort defenders, and they gathered around the flag. The struggle was now a hand-to-hand one, in which nothing but soft snow was used, and nearly every boy had his face washed. "Get back there!" roared Danny Rugg, who was close to the flag, but as he spoke two boys shoved him down on his face in the snow, and the next moment Bert and another boy of the invading party had the flag and was carrying it away in triumph. "The fort has fallen!" screamed Nan, and clapped her hands.