August 7 It was not until the first week in August that Scott was able to move upon the capital. The army now numbered 14,000 men. Several hundred were sick in hospital, and 600 convalescents, together with 600 effectives, were left to garrison Puebla. The field force was organised in four divisions: the first, under Major-General Worth; the second, under Major-General Twiggs; the third, to which Magruder’s battery was attached, under Major-General Pillow; the fourth (volunteers and marines), under Major-General Pierce. Four field batteries, a small brigade of dragoons, and a still smaller siege train[[8]] made up a total of 11,500 officers and men. During the three months that his enemy was idle at Puebla, Santa Anna had reorganised his army; and 30,000 Mexicans, including a formidable body of cavalry, fine horsemen and well trained,[[9]] and a large number of heavy batteries, were now ready to oppose the advance of the invaders.
On August 10 the American army crossed the Rio Frio Mountains, 10,000 feet above the sea, the highest point between the Atlantic and the Pacific, and as the troops descended the western slopes the valley of Mexico first broke upon their view. There, beneath the shadow of her mighty mountains, capped with eternal snows, stood
The Imperial city, her far circling walls,
Her garden groves, and stately palaces.
There lay the broad plain of Tenochtitlan, with all its wealth of light and colour, the verdure of the forest, the warmer hues of the great corn-fields, ripening to the harvest, and the sheen and sparkle of the distant lakes. There it lay, as it burst upon the awe-struck vision of Cortez and his companions, “bathed in the golden sunshine, stretched out as it were in slumber, in the arms of the giant hills.”
On every hand were the signs of a teeming population. White villages and substantial haciendas glistened in the woodlands; roads broad and well-travelled crossed the level; and in the clear atmosphere of those lofty altitudes the vast size of the city was plainly visible. The whole army of Mexico formed the garrison; hills crowned with batteries commanded the approaches, while a network of canals on either flank and a broad area of deep water enhanced the difficulties of manœuvre. The line of communication, far too long to be maintained by the small force at Scott’s disposal, had already been abandoned. The army depended for subsistence on what it could purchase in the country; the sick and wounded were carried with the troops, and there was no further reserve of ammunition than that which was packed in the regimental waggons. Cortez and his four hundred when they essayed the same enterprise were not more completely isolated, for, while the Spaniard had staunch allies in the hereditary foes of the Aztecs, Scott’s nearest supports were at Puebla, eighty miles from Mexico, and these numbered only 1,200 effective soldiers. The most adventurous of leaders might well have hesitated ere he plunged into the great valley, swarming with enemies, and defended by all the resources of a civilised State. But there was no misgiving in the ranks of the Americans. With that wholesome contempt for a foreign foe which has wrought more good than evil for the Anglo-Saxon race, the army moved forward without a halt. “Recovering,” says Scott, “from the trance into which the magnificent spectacle had thrown them, probably not a man in the column failed to say to his neighbour or himself, ‘That splendid city shall soon be ours!’”
The fortifications which protected Mexico on the east were found to be impregnable. The high ridge of El Penon, manned by nearly the whole of Santa Anna’s army, blocked the passage between the lakes, and deep morasses added to the difficulties of approach. To the south, however, on the far side of Lake Chalco, lay a more level tract, but accessible only by roads which the Mexicans deemed impracticable. Despite the difficulties of the route, the manœuvre of Cerro Gordo was repeated on a grander scale.
August 16–18 After a toilsome march of seven-and-twenty miles from Ayotla, over the spurs of the sierras, the troops reached the great road which leads to the capital from the south. Across this road was more than one line of fortifications, to which the Mexican army had been hurriedly transferred. The hacienda of San Antonio, six miles from the city, strengthened by field-works and defended by heavy guns, commanded the highway. To the east was a morass, and beyond the morass were the blue waters of Lake Chalco; while to the west the Pedregal, a barren tract of volcanic scoriæ, over whose sharp rocks and deep fissures neither horse nor vehicle could move, flanked the American line of march. The morass was absolutely impassable. The gloomy solitude of the Pedregal, extending to the mountains, five miles distant, seemed equally forbidding; but the engineer officers came once more to the rescue. A road across the Pedregal, little better than a mule track, was discovered by Captain Lee.
August 19 Under cover of a strong escort it was rapidly improved, and Pillow’s and Worth’s divisions, accompanied by Magruder’s battery, were directed to cross the waste of rocks. Beyond the Pedregal was a good road, approaching the city from the south-west; and by this road the post of San Antonio might be assailed in rear.
Overlooking the road, however, as well as the issues from the Pedregal, was a high ridge, backed by the mountains, and held by 6,000 Mexicans. Opposite this ridge the Americans came out on cultivated ground, but all further progress was completely checked. Shortly after midday the leading brigade, with Magruder’s battery on hand, reached the summit of a hill within a thousand yards of the enemy’s breastworks. Magruder came at once into action, and the infantry attempted to push forward. But the Mexican artillery was far superior, both in number of pieces and weight of metal, and the ground was eminently unfavourable for attack. Two-and-twenty heavy cannon swept the front; the right of the position was secured by a deep ravine; masses of infantry were observed in rear of the intrenchments, and several regiments of lancers were in close support. For three hours the battle raged fiercely. On the right the Americans pushed forward, crossing with extreme difficulty an outlying angle of the Pedregal, covered with dense scrub, and occupied the village of Contreras. But elsewhere they made no impression. They were without cavalry, and Magruder’s guns were far too few and feeble to keep down the fire of the hostile batteries. “The infantry,” says Scott, “could not advance in column without being mowed down by grape and canister, nor advance in line without being ridden down by the enemy’s numerous horsemen.” Nor were the Mexicans content on this occasion to remain passively in their works. Both infantry and cavalry attempted to drive the assailants back upon the Pedregal; and, although these counterstrokes were successfully repulsed, when darkness fell the situation of the troops was by no means favourable. Heavy columns of Mexicans were approaching from the city; the remainder of the American army was opposite San Antonio, five miles distant, on the far side of the Pedregal, and no support could be expected. To add to their discomfort, it rained heavily; the thunder crashed in the mountains, and torrents of water choked the streams. The men stood in the darkness drenched and dispirited, and an attack made by a Mexican battalion induced General Pillow to withdraw Magruder’s battery from the ridge. The senior subaltern had been killed. 15 gunners and as many horses had fallen. The slopes were covered with huge boulders, and it was only by dint of the most strenuous exertions that the guns were brought down in safety to the lower ground.
A council of war was then held in Contreras Church, and, contrary to the traditionary conduct of such conventions, a most desperate expedient was adopted. The Mexican reinforcements, 12,000 strong, had halted on the main road, their advanced guard within a few hundred yards of the village. Leaving two regiments to hold this imposing force in check, it was determined to make a night march and turn the rear of the intrenchments on the ridge. The Commander-in-Chief was beyond the Pedregal, opposite San Antonio, and it was necessary that he should be informed of the projected movement.