As these and other arriving troops from Daiquiri began moving inland, the dismounted cavalry under General Wheeler and the infantry under General Lawton moved ahead of them, following the main routes to Santiago. General Wheeler's two brigades of dismounted cavalry made camp at El Pozo, to the northwest of Siboney and less than five miles from Santiago. This force included Colonel Henry Carroll's three regiments (3d, 6th and 9th US Cavalries) and the newly promoted Brigadier General Leonard Wood's brigade consisting of the 1st US Cavalry, the all-Black 10th US Cavalry, and Colonel Roosevelt's Rough Riders (1st US Volunteer Cavalry). Strung out along the Santiago road from El Pozo to Siboney and east to Daiquiri were the men of Brigadier General J. Ford Kent's 1st Infantry Division.
By the last day of June, the first soldiers to land on Cuban shores had already endured more than a week of the temperamental tropical climate, and several had become ill. More than a century earlier Yellow Fever and other tropical ailments had thwarted the British forces in Cuba, and General Shafter was eager to press his attack before it could take a greater toll on his on men.
On June 30th General Shafter rode his horse to El Pozo to plan his attack. Joined by most of his command staff, he made a personal reconnaissance while his chief engineer officer Lieutenant Colonel George McClellan Derby surveyed the Spanish positions from a large balloon. Most of the enemy soldiers were stationed in and immediately around the city of Santiago, a force of some 10,000 well entrenched Spanish soldiers and marines under General Arsenio Linares y Pombo. To the west of the city, Cuban General Calixto Garcia Iniguez blocked any reinforcement of the Spaniards from the inland which, when coupled with the US Naval blockade of the harbor entrance, virtually isolated the Spanish ground forces as well as Admiral Cervera's squadron of ships.
General Shafter concluded that the key to taking Santiago lay first in taking the heights overlooking the city from the east. The high ridgeline, just north of the small city of San Juan and west of the San Juan River, was known as San Juan Hill. Rising up from the jungle below, the hill was well defended by 750 Spanish soldiers in heavily fortified positions, and dominated by large blockhouses. Two modern howitzers provided artillery support as well. If the Americans could take and hold this position, they would have a commanding view and a tactical advantage over the 10,000 enemy in the city below.
His reconnaissance completed, General Shafter met with General Kent of the 1st Division and Brigadier General Samuel Sumner, who had taken command of the cavalry after General Wheeler had fallen ill, to outline his battle plan. On the following morning Kent would move his forces to storm and capture San Juan Hill, flanked on the right by Sumner's cavalry. To prevent the enemy from sending reinforcements to San Juan Hill from their garrison at El Caney to the North, General Lawton would march his infantry to capture the city, then pull back to reinforce General Sumner's cavalry on the north end of the heights. General Lawton predicted that it would take about two hours to accomplish his first mission, thus his soldiers would engage the enemy first while the attack at San Juan was held back until he had taken the city.
As the early morning assault at El Caney turned into continued battled throughout the afternoon, the main force under Generals Sumner and King could wait no longer. Without the flanking support of General Lawton's Division, the order was given to advance towards San Juan Hill. And there this force would find a similarly stiff resistance.
Shortly after Captain Grimes battery concluded its 8:00 A.M. initial 45-minute barrage on San Juan Hill, General McClernand rode to the front to meet with General Kent. Pointing towards the blockhouse that dominated the heights of San Juan hill he told the commander of the 1st Infantry Division to prepare his men to take the position. Meanwhile, he ordered the Cavalry forward and to the right "to connect with Lawton"...unaware that Lawton's men would spend the entire day fighting for survival and victory at El Caney. While the infantry held its position, General Sumner's two brigades moved down the jungle trails, past the infantry and towards the San Juan valley and the river crossing. Along their route they were subjected to constant sniper fire from the surrounding jungles, and casualties mounted long before the anticipated assault could be ordered.
Behind General Wood's brigade, four men towed a large balloon from which Lieutenant Colonel Derby and Signal Corps Major Joseph Maxfield scanned the terrain. It was a bad mistake with significant consequences. While the observation balloon gave Derby and Maxfield a good sense of the friendly movements, the enemy positions, and the preferable routes to their objective, it also broadcast to the enemy the exact position and movement of the cavalry. The Spanish zeroed in on the balloon from the heights as well as from the jungle below, and released a torrent of leaden death; most of which fell on the soldiers below. As the balloon came under fire, it gradually descended; directly in the middle of the 1st and 10th Cavalry as they forded the river. Attracting enemy fire like a magnet, the result was immediate, devastating, and tragic.
Astride his pony Texas, Colonel Roosevelt hurried his regiment across the knee-deep ford of the San Juan River and into position below San Juan Hill. Slightly forward of the Rough Riders were the soldiers of Colonel Henry K. Carroll's 1st Brigade, lined up for assault with the 6th US Cavalry in the center, flanked on the right by the Buffalo Soldiers of the 9th Cavalry and on the left by the 3rd Cavalry. Coming up from behind to take a position to the left of the Rough Riders was the 1st US (Regular) Cavalry Regiment, followed by the 10th Cavalry.
The high ridge that was known as San Juan Hill was actually two hilltops, separated by a slight ravine. The southernmost point was most recognizable for the blockhouse that dominated the crest. Across the ravine to the north was another large blockhouse, and this hill would come to be known as KETTLE HILL. By 11 o'clock most of the 15 regiments tasked with wresting control of the two hills had crossed the San Juan River and were prepared for the assault. Below San Juan Hill the soldiers of General Kent's Division continued to return fire on the enemy as they awaited orders. To the Division's right the dismounted cavalry was poised to attack Kettle Hill. Despite his illness, the venerable General Fighting Joe Wheeler rode his horse to the front to watch his men, now under the leadership of General Sumner, fight their way through the blockhouses and enemy trenches to reach the top of Kettle Hill.