Notwithstanding the severe drain on his forces by this incessant warfare, the young monarch contrived to relieve them in some degree by different detachments, which took the place of one another. This was apparent from the different uniforms and military badges of the Indian battalions that successively came and disappeared from the field. At night a strict guard was maintained in the Aztec quarters, a thing not common with the nations of the plateau. The outposts of the hostile armies were stationed within sight of each other. That of the Mexicans was usually placed in the neighborhood of some wide breach, and its position was marked by a large fire in front. The hours for relieving guard were intimated by the shrill Aztec whistle, while bodies of men might be seen moving behind the flame, which threw a still ruddier glow over the cinnamon-colored skins of the warriors. While thus active on land, Guatemozin was not idle on the water. He was too wise, indeed, to cope with the Spanish navy again in open battle; but he resorted to stratagem, so much more congenial to Indian warfare. He placed a large number of canoes in ambuscade among the tall reeds which fringed the southern shores of the lake, and caused piles, at the same time, to be driven into the neighboring shallows. Several _piraguas_, or boats of a larger size, then issued forth, and rowed near the spot where the Spanish brigantines were moored. Two of the smallest vessels, supposing the Indian barks were conveying provisions to the besieged, instantly stood after them, as had been foreseen. The Aztec boats fled for shelter to the reedy thicket where their companions lay in ambush. The Spaniards, following, were soon entangled among the palisades under the water. They were instantly surrounded by the whole swarm of Indian canoes, most of the men were wounded, several, including the two commanders, slain, and one of the brigantines fell--a useless prize--into the hands of the victors. Among the slain was Pedro Barba, captain of the crossbowmen, a gallant officer, who had highly distinguished himself in the Conquest. This disaster occasioned much mortification to Cortés. It was a salutary lesson, that stood him in good stead during the remainder of the war.[33] Thus the contest was waged by land and by water,--on the causeway, the city, and the lake. Whatever else might fail, the capital of the Aztec empire was true to itself, and, mindful of its ancient renown, opposed a bold front to its enemies in every direction. As in a body whose extremities have been struck with death, life still rallied in the heart, and seemed to beat there, for the time, with even a more vigorous pulsation than ever.