The Philippine-American War was an armed conflict between the 
First Philippine Republicball and 
USAball.
Background
During the 14th century, Portugalball had a headstart in naval navigation and managed to acquire spice trade due to several factors, including the Ottomans banning Europe from spice trade and the Portuguese wanting to boost their economy. Being competitive, Spainball also conducted several expeditions to find India westward. Although they failed to rich India and instead found the Americas, they started conquering it due to the large silver reserves.
In 1519, wanting to find the "Spice Islands" in modern-day Moluccas, Spain dispatched a fleet of 5 ships and 270 men to find the islands. It is led by a Spanish Portuguese dude named Ferdinand Magellan(Portuguese: Fernão de Magalhães, Spanish: Fernando de Magallanes). After 2 years of sailing, they finally reached the Philippines and converted some local natives. However, a chieftain refused to convert his people and himself to Catholic faith and that is Lapu-Lapu. Magellan went into battle with his 60 fully-armoured conquistadors but his army was bogged down in the coast and Magellan himself didn't survived the battle. The fleet managed to reach their destination and managed to collect some spices. However, only 21 men managed to get to Spain and only 1 ship also returned to Spain.
After the expedition, Charles I, King of Spain, sent more expeditions but later gave up due to the large amounts of money needed to fund the project and also since travelling to the Moluccas Islands was already a hell-rated challenge to sail.
After Charles I died, his son, Philip II, dispatched another expedition to the Philippines. This expedition was led by Miguel Lopez de Legazpi and he is accompanied with 4-5 ships with 380-500 men. Using New Spain(Mexicoball) as their starting point, they finally colonized the Philippines after some struggle and this also shortened the route to those sexy islands, as it only took them 4 months to sail unlike starting from Spain, which took Magellan and his buddies 2 years.
However, the native Filipinos weren't happy with the colony rules, such as high taxes and Spanish language is the only language legal to speak. The Filipinos rebelled constantly but all were brutally suppressed. Also, the Philippines was threatened by foreign powers. This included Chinese and Japanese wokou pirates and also met heavy resistance by some locals that was initially not conquered by Spain during the Lopez expedition, this included the Zambal people in modern-day Zambales, Igorot people in the Cordilleran mountains and the last but not the least, the Moro people from the Muslim sultanates centered in present-day Mindanao.
In 1892, the Katipunan or KKK was founded by Andres Bonifacio, it's an organization formed to rise up against the Spanish government based in the Philippines. Fighters in Cavite province won early victories. One of the most influential and popular leaders from Cavite was Emilio Aguinaldo, mayor of Cavite El Viejo (modern-day Kawit), who gained control of much of the eastern portion of Cavite province. Eventually, Aguinaldo and his faction gained control of the leadership of the Katipunan movement.
However, this caused a divide between the KKK. There were 2 major factions in the Katipunan which are the Magdiwang and Magdalo, led by Bonifacio and Aguinaldo respectively. The Magdalo later gained the upperhand and dominated the KKK, executing Bonifacio because of the so-called "treason". Aguinaldo also was elected president by the newly-formed Philippine revolutionary government.
However, the loss of Bonifacio greatly weakened the KKK. The Spanish used this weakness to strengthen their position and managed to defeat the revolutionaries in quick succession. Cavite was captured and Aguinaldo entrenched himself in the mountains of Central Luzon.
The Spanish Governor-General, Primo de Rivera, arranged a meeting with Aguinaldo and his cabinet. They signed an armistice. On December 4, 1897, they signed the Treaty of Biak-na-Bato, where Aguinaldo and his buddies will exile themselves in Hong Kong while the Spanish will pay him $800,000, to be payed in two installments(Aguinaldo received only the first installment, costing $400,000-600,000 while he never received the second one). Before departing, Aguinaldo announced the fighting rebels to surrender but despite this, the rebels still continued to fight, due to mistreatment.
After four months in exile, Aguinaldo decided to resume his role in the Philippine Revolution. He departed from Singapore aboard the steamship Malacca on April 27, 1898. He arrived in Hong Kong on May 1, the day that US Commodore George Dewey's naval forces destroyed Rear-Admiral Patricio Montojo's Spanish Pacific Squadron at the Battle of Manila Bay. Aguinaldo departed Hong Kong aboard the USRC McCulloch on May 17, arriving in Cavite on May 19.
Less than three months after Aguinaldo's return, the Philippine Revolutionary Army had conquered nearly all of the Philippines. With the exception of Manila, which was surrounded by revolutionary forces some 12,000 strong, the Filipinos controlled the Philippines. Aguinaldo turned over 15,000 Spanish prisoners to the Americans, offering them valuable intelligence.[citation needed] Aguinaldo declared independence at his house in Cavite El Viejo on June 12, 1898.
The Philippine Declaration of Independence was not recognized by either the United States or Spain, and the Spanish government ceded the Philippines to the United States in the 1898 Treaty of Paris, which was signed on December 10, 1898, in consideration for an indemnity for Spanish expenses and assets lost. On January 1, 1899, Aguinaldo was declared President of the Philippines—the only president of what would be later called the First Philippine Republic. He later organized a congress in Malolos, Bulacan to draft a constitution.
Origins of the conflict
On April 22, 1898, Aguinaldo had a private meeting with E. Spencer Pratt, the consul of US in Singapore, after the meeting, Aguinaldo again decided to lead the revolution. He however, had some doubts and asked the consul if they needed to sign a treaty. However, Pratt said no as the word of the consul is equal to the word of the president in U.S. With these assurances, the general and his buddies left for the Philippines.
Filipino historian Teodoro Agoncillo writes of "American apostasy", saying that it was the Americans who first approached Aguinaldo in Hong Kong and Singapore to persuade him to cooperate with Dewey in wresting power from the Spanish. Conceding that Dewey may not have promised Aguinaldo American recognition and Philippine independence (Dewey had no authority to make such promises), he writes that Dewey and Aguinaldo had an informal alliance to fight a common enemy, that Dewey breached that alliance by making secret arrangements for a Spanish surrender to American forces, and that he treated Aguinaldo badly after the surrender was secured. Agoncillo concludes that the American attitude towards Aguinaldo "... showed that they came to the Philippines not as a friend, but as an enemy masking as a friend."
The Filipino forces began besieging Intramuros, the fortress where Spanish soldiers entrenched themselves. Not wanting to be ashamed as they were beaten by some rebels out of one of their last major colonies, the Spanish arranged a meeting with Commodore Dewey and Brig. Gen. Wesley Merritt. During the meeting, they agreed that the Spanish will only surrender to the Americans. To save face, the Spanish surrender would take place after a mock battle in Manila which the Spanish would lose; the Filipinos would not be allowed to enter the city. On the eve of the battle, Brigadier General Thomas M. Anderson telegraphed Aguinaldo, "Do not let your troops enter Manila without the permission of the American commander. On this side of the Pasig River you will be under fire." On August 13, American forces captured the city of Manila from the Spanish.
War
On the evening of Febuary 4, 1899, Private William Grayson of the 1st Nebraska Volunteer Infantry Regiment started the war when he fired his rifle at 2 Filipino soldiers. According to Filipino sources, the soldiers slain were unarmed. This action triggered the 1899 Battle of Manila. The following day, Filipino General Isidoro Torres came through the lines under a flag of truce to deliver a message from Aguinaldo to General Otis that the fighting had begun accidentally, and that Aguinaldo wished for the hostilities to cease immediately and for the establishment of a neutral zone between the two opposing forces. Otis dismissed these overtures, and replied that the "fighting, having begun, must go on to the grim end". On February 5, General Arthur MacArthur ordered his troops to advance against Filipino troops, beginning a full-scale armed clash. The first Filipino fatality of the war was Corporal Anastacio Felix of the 4th Company, Morong Battalion under Captain Serapio Narváez. The battalion commander was Colonel Luciano San Miguel.
On February 11, 1899—one week after the first shots of the war were fired—American naval forces destroyed the city of Iloilo by bombardment from the USS Petrel and the USS Baltimore. The city was captured by ground forces led by Brigadier General Marcus Miller, with no loss of American lives.
Months later, after finally securing Manila from the Filipino forces, American forces moved northward, engaging in combat at the brigade and battalion level in pursuit of the fleeing insurgent forces and their commanders. The Filipinos were no-match for the well-trained and well-equipped U.S Army but despite knowing this, many commanders still engage the Americans in conventional warfare.
A brilliant Filipino general named Antonio Luna proposed to Aguinaldo the utilization of guerrilla warfare tactics. However, Aguinaldo refused to wage guerilla warfare and instead constantly retreated with no plans in his head and continued to engage the Americans in conventional warfare.
On June 5, 1899, Luna was assassinated by the Kawit battalion, a battalion known for having close ties with Aguinaldo himself. Up until now, Luna's assassination is still a matter of debate whether he was assassinated by Aguinaldo's orders or the men simply acted independently on their own. The assassins also never got captured.
The death of Luna was a decisive blow to the Philippine Republican Army. They lost their most brilliant general and Aguinaldo suffered defeat after defeat after defeat in the battlefield and also forced him to change his headquarters constantly. On November 1899, he finally accepted guerrilla warfare as the main strategy and ordered his army to retreat to the mountains. From then on, the Filipinos would stage on bloody ambushes which inflicted heavy casualties to the Americans which doesn't know the terrain well.
On December 2, 1899, a Filipino force of 60 men under the command of Gen. Gregorio del Pilar managed to delay the Americans in the Tirad pass for a short while in, buying Aguinaldo enough time to escape. The defenders were finally overran when an Igorot showed them a secret passage which can encircle the defenders. 52 Filipinos were killed, including del Pilar.
On March 23, 1901, General Frederick Funston and his troops captured Aguinaldo in Palanan, Isabela, with the help of some Filipinos (called the Macabebe Scouts after their home locale) who had joined the Americans' side. The Americans pretended to be captives of the Scouts, who were dressed in Philippine Army uniforms. Once Funston and his "captors" entered Aguinaldo's camp, they immediately fell upon the guards and quickly overwhelmed them and the weary Aguinaldo.
On April 1, 1901, at the Malacañan Palace in Manila, Aguinaldo swore an oath accepting the authority of the United States over the Philippines and pledging his allegiance to the American government. On April 19, he issued a Proclamation of Formal Surrender to the United States, telling his followers to lay down their weapons and give up the fight.
The capture of Aguinaldo dealt a severe blow to the Filipino cause, but not as much as the Americans had hoped. General Miguel Malvar took over the leadership of the Filipino government, or what remained of it. He originally had taken a defensive stance against the Americans, but now launched all-out offensive against the American-held towns in the Batangas region. General Vicente Lukbán in Samar, and other army officers, continued the war in their respective areas.
General Bell relentlessly pursued Malvar and his men, forcing the surrender of many of the Filipino soldiers. Finally, Malvar surrendered, along with his sick wife and children and some of his officers, on April 16, 1902. By the end of the month nearly 3,000 of Malvar's men had also surrendered. With the surrender of Malvar, the Filipino war effort began to dwindle even further.
The Philippine Organic Act—approved on July 1, 1902—codified President McKinley's previous executive order which had established the Second Philippine Commission. The act also stipulated that a legislature would be established composed of a popularly elected lower house, the Philippine Assembly, and an upper house consisting of the Philippine Commission. The act also provided for extending the United States Bill of Rights to Filipinos. On July 2, the United States Secretary of War telegraphed that since the insurrection against the United States had ended and provincial civil governments had been established throughout most of the Philippine archipelago, the office of military governor was terminated. On July 4, Theodore Roosevelt, who had succeeded to the U.S. presidency after the assassination of President McKinley, proclaimed an amnesty to those who had participated in the conflict.
War strategies
Filipino strategies
The Filipinos managed to raise an army of between 80,000-100,000 soldiers at its peak. This army were accompanied by tens of thousands of auxiliaries.
The Filipinos were short on modern weapons, such as rifles and artillery pieces. Most were just armed with bolos(Filipino machete) and spears which were vastly inferior to American weapons.
However, the Filipinos were smart and can cope up with the meta. Using their extensive knowledge of terrain in the Philippines(which is known to be mountainous and have lots of forests), they used ambushes, hit-and-run tactics, sabotages and more to make the occupation of the U.S more difficult over the years. In the early months of the guerrilla phase, the Americans already had ~500 casualties. The Philippine Army began staging bloody ambushes and raids, such as the guerrilla victories at Paye, Catubig, Makahambus, Pulang Lupa, Balangiga and Mabitac. At first, it seemed that the Filipinos might be able to fight the Americans to a stalemate and force them to withdraw. President McKinley considered withdrawal when the guerrilla raids began.
The Filipino operational center of gravity was the ability to sustain its force of 100,000 irregulars in the field. The Filipino general Francisco Macabulos described the Filipinos' war aim as, "not to vanquish the U.S. Army but to inflict on them constant losses." In the early stages of the war, the Philippine Revolutionary Army employed the conventional military tactics typical of an organized armed resistance. The hope was to inflict enough American casualties to result in McKinley's defeat by William Jennings Bryan in the 1900 presidential election. They hoped that Bryan, who held strong anti-imperialist views, would withdraw the American forces from the Philippines.
McKinley's election victory in 1900 was demoralizing for the insurgents, and convinced many Filipinos that the United States would not depart quickly. Coupled with a series of devastating losses on the battlefield against American forces equipped with superior technology and training, Aguinaldo became convinced that he needed to change his approach. Beginning on September 14, 1899, Aguinaldo accepted the advice of General Gregorio del Pilar and authorized the use of guerrilla warfare tactics in subsequent military operations in Bulacan.
American strategies
During the early stages of the war, the Americans only had less than 20,000 troops. But despite this, they were equipped with superior weapons and were very well-trained. Using this advantages, they were able to inflict crushing defeats on the Filipino soldiers, heavily demoralizing them.
The Americans did a lot of atrocities during their invasion of the Philippines. They massacred the Philippines cruelly, according to the American officers, every one American killed is equal to 10 Filipino lives, thus it became a U.S habit of killing captured Filipino soldiers or massacring natives. They also torture the Filipinos using the water cure, where the victim were forced to drink lots of water, causing water intoxication or worse, death.
In retaliation for their defeat against Filipino forces in Balangiga, American forces masaccred every Filipino male in Samar, General Jacob Smith, arriving in Samar with fresh reinforcements, famously stated:
"I want no prisoners. I wish you to kill and burn; the more you kill and burn, the better it will please me... The interior of Samar must be made a howling wilderness..."
