THE young Republic survived with difficulty an Etruscan JL attempt to restore the expelled royal house (510 B.C.). Soon after this date, the Etruscan power began to decline under repeated Gallic raids. Rome herself was sacked by the Gauls in 390 B.C., but bought them off. The city's chief enemies were the tribes on the foothills of the Apennines, and on the plain to the south. She fought them again and again and beat them one after the other. To hold them down, she started building military roads, and establishing colonies, detached portions of Rome, at strategic points. Her own allies in the Latin League of cities in the region south of Rome, feeling themselves overshadowed, tried conclusions with her in vain (338 B.C.). The conquered cities were not allowed to have direct relations with each other, either in politics or trade or marriage. This was the famous policy of " divide and conquer," which not only kept the cities apart but made Rome a centre of trade for them all. By chance, in the fourth century B.C., Rome evolved a method of government which was new in world history- the method of gradual incorporation in the Roman State. The Italian communities were first given private rights of marriage and trade with Rome, combined with the duty of military service. Later on they might receive " Latin rights " which included the privilege of becoming full citizens by settling at Rome. The last stage was the grant of full citizenship. Athens had failed because she did not take her subjects into partnership. Rome made her citizenship a desirable privilege which loyalty could win. At first she imposed it by force and the victims objected to losing their national identity. Then, when the profits of success came to be distributed, the tribes clamoured for admission, and fought with her because it was denied. The Roman Empire succeeded by bringing its subjects under one universal rule. The British Empire, on the other hand, maintains itself by training its subjects for self-government, a more difficult, though a higher and more fruitful achievement. By the year 280 B.C., Roman conquests had reached the hills overlooking the Po valley. Then after beating Pyrrhus, exponent of the highest military science of the Greeks, who had come to help the Greek cities of the South against her, she annexed the rest of Italy down to the Straits of Messina (266 B.C.)