In January 1898, fearing the fate of American interests in Cuba due to the war, the cruiser USS Maine was dispatched to protect them.

The Americans, after already landing troops in the Battle of Guantánamo Bay, moved inland to seek a decisive encounter with the Spanish forces.

Both sides drew blood at the Battle of Las Guasimas, with the Spanish moving to defend the strategically valuable San Juan Heights from the Americans.

A week later, a significantly larger American force, including the famed 'Rough Riders', moved to clear the heights of the Spanish.

After enduring artillery fire which inflicted heavy casualties, the Americans charged up the hill and dispersed the Spanish, suffering even more heavily in the process.

The battle also proved to be the location of the "greatest victory" for the Rough Riders, as stated by the press and its new commander, Theodore Roosevelt.

[5] The Americans won another engagement at El Caney the same day, with both battles highlighting the bravery and skill of the American/Cuban forces, as well as the Spanish defenders.

For unclear reasons, Linares failed to reinforce this position, choosing to hold nearly 10,000 Spanish reserves in the city of Santiago de Cuba.

This meant that the fire from the Spanish troops would have difficulty hitting the advancing enemy when the attacking Americans reached the defilade at the foot of the heights.

Once they began scaling the hill, however, the attackers would be in full view of the defenders, who could engage the Americans with both rifle and artillery fire.

[6][page needed] Most Spanish troops were recently arrived conscripts, but their officers were skilled in fighting Cuban insurgents.

[7] The American regular forces and troopers were armed with bolt-action Krag rifles chambered in the smokeless .30 Army caliber.

However, U.S. 3.2-inch artillery pieces were of an outmoded design, with a slow rate of fire due to bag powder charges and lack of a recoil mechanism.

[9] Shafter's plans to attack Santiago de Cuba called for Lawton's division to move north and reduce the Spanish stronghold at El Caney, a task which was to take about two hours.

Shafter, too ill to personally direct the operations, set up his headquarters at El Pozo 2 mi (3.2 km) from the heights and communicated via mounted staff officers.

"[6][page needed] Lt. Ord then asked the leaders to the right of the 10th Cavalry (members of the 3rd and 1st Volunteers) to "support the regulars" when they charged the heights.

When Ord returned to his assigned unit, he advised his commander, Captain John Bigelow Jr. of D Troop, of his conversation with the general.

Witnessing the assault on San Juan Hill, more than one observer from the U.S. side noticed some of the Spanish defenders fleeing their trenches to escape the intense fire.

[6][page needed] At 13:50, Private Arthur Agnew of the 13th Infantry pulled down the Spanish flag atop the San Juan blockhouse.

A Spanish counter-attack was launched late in the afternoon, but was easily beaten back with the aid of supporting Gatling fire from San Juan Hill.

[17]During the battle, Parker's Gatling guns expended approximately 18,000 rounds in eight and a half minutes (over 700 rounds per minute of continuous fire) into the Spanish defensive lines atop the heights, killing many of the defenders and forcing others to flee the trench lines, while disrupting the aim of any still alive who continued to resist.

[32] General Linares's troops on San Juan heights fired on the newly won American position on the crest of Kettle Hill.

Kent sent forward the 3rd Infantry Brigade, now effectively commanded by Lt. Col. Ezra P. Ewers,[33] to join the advance, which had successfully reached the heights.

General Sumner intercepted Roosevelt and angrily ordered him to return to Kettle Hill immediately to prepare for the expected counterattack.

[15][38][non-primary source needed][39] After the counterattack was driven off, Lt. Parker moved to Kettle Hill to view the American positions, where he was soon joined by Sgt.

[40][non-primary source needed] Miley (who was primarily tasked with inspecting troop positions for General Shafter) had restrained Weigle's crew from opening fire during the entirety of the fighting.

[40][non-primary source needed] Returning to the two Gatlings on San Juan Hill, Lt. Parker had the guns relocated near the road to avoid counter-battery fire.

[15][40][non-primary source needed] Parker located the enemy gun and trained the two Gatlings using a powerful set of field glasses.

[15][40][non-primary source needed] July 4, Parker ordered his three operational guns moved into the battle line around the city of Santiago.

In view of the large number of U.S. casualties incurred from small-arms fire, the Army decided to update and modernize its small arms arsenal.