The allies for some time found sufficient occupation for their arms in their own valley; but they soon overleaped its rocky ramparts, and by the middle of the fifteenth century, under the first Montezuma, had spread down the sides of the table-land to the borders of the Gulf of Mexico. Tenochtitlan, the Aztec capital, gave evidence of the public prosperity. Its frail tenements were supplanted by solid structures of stone and lime. Its population rapidly increased. Its old feuds were healed. The citizens who had seceded were again brought under a common government with the main body, and the quarter they occupied was permanently connected with the parent city; the dimensions of which, covering the same ground, were much larger than those of the modern capital of Mexico.[38][39] Fortunately, the throne was filled by a succession of able princes, who knew how to profit by their enlarged resources and by the martial enthusiasm of the nation. Year after year saw them return, loaded with the spoils of conquered cities, and with throngs of devoted captives, to their capital. No state was able long to resist the accumulated strength of the confederates. At the beginning of the sixteenth century, just before the arrival of the Spaniards, the Aztec dominion reached across the continent, from the Atlantic to the Pacific, and, under the bold and bloody Ahuitzotl, its arms had been carried far over the limits already noticed as defining its permanent territory, into the farthest corners of Guatemala and Nicaragua. This extent of empire, however limited in comparison with that of many other states, is truly wonderful, considering it as the acquisition of a people whose whole population and resources had so recently been comprised within the walls of their own petty city, and considering, moreover, that the conquered territory was thickly settled by various races, bred to arms like the Mexicans, and little inferior to them in social organization. The history of the Aztecs suggests some strong points of resemblance to that of the ancient Romans, not only in their military successes, but in the policy which led to them.[40]