[7] He was enrolled at the Ateneo Municipal de Manila at the age of 15, where he was rated good in Latin, Greek, Spanish, and French, middling in philosophy, and excellent in arithmetic and algebra.

[5] During his studies in the Ateneo, he stayed in the house of his paternal aunt, Hilaria H. del Pilar, and her husband, the propagandist Deodato Arellano.

There was one incident in Malolos, where del Pilar stole copies of the book Cuesteones de sumo interes from the parish priest, Father Felipe García, who had a habit of distributing counter-revolutionary materials after mass.

[7] At the onset of the revolution, and in response to reports of "successive triumphs" in Cavite, some 3,000 revolutionary forces marched to seize the town of Paombong, Bulacan, forming a military government.

[5] Del Pilar was eventually assigned to the forces of Eusébio Roque (also known as Maestrong Sébio) in Kakarong de Sili, a fort near the town of Pandi.

On New Year's Day, 1897, del Pilar participated in the defense of Kakarong de Sili, managing to escape with only nine others before the Spaniards overran the fort.

[5] Del Pilar's success in Paombong caught the attention of Emilio Aguinaldo, who promoted the captain to a lieutenant colonel, eventually earning his trust and being let into his inner circle of confidants.

When negotiations with the Spanish took place in the which concluded with the signing of the Pact of Biak-na-Bato, Aguinaldo took del Pilar with him to exile in Hong Kong.

[7] The exiles in Hong Kong organized a Supreme Council, electing del Pilar to a position second only to Tomás Mascardo.

[5][10] After the Americans defeated the Spanish in the Battle of Manila Bay, Aguinaldo, del Pilar, and other exiled leaders returned to the Philippines.

[11] On del Pilar's return to the Philippines, he set out to liberating his home province of Bulacan, eventually accepting Spanish surrender on June 24, 1898.

[12] Del Pilar was then called to relieve the wounded General Pantaleon García and continue operations in Caloocan, ultimately succeeded on August 13, 1898.

[7] When the Philippine–American War broke out in February 1899, following the cession of the Philippines by Spain to the United States in the Treaty of Paris of 1898, del Pilar fought alongside General Antonio Luna in Manila, suffering heavy casualties.

At the headquarters of General Luna it was learned that his gentleman spent days and nights at fiestas and dances which his flatterers offered in his honor.

Del Pilar, for his part, led his troops to a victory over Major Franklin Bell in the first phase of the Battle of Quingua (modern-day Plaridel, Bulacan) on April 23, 1899.

Luna, however, had left the battle to punish General Tomás Mascardo for insubordination, leaving del Pilar with the defense of the Bagbag River.

[14] On June 4, 1899, del Pilar joined Aguinaldo in San Isidro and received orders to capture Antonio Luna, dead or alive, on charges of high treason.

Word had come that the Americans were advancing on Tirad Pass in an effort to cut off Aguinaldo from the Tinio Brigade situated on the Abra River.

The US Army 33rd Infantry Regiment, under Major Peyton C. March took Concepción on December 1 and began to scale Tirad Pass the next day.

After the battle, del Pilar's belongings were taken by the Americans as war trophies, including a handkerchief embroidered with the name Dolores, a locket with a picture of a girl, and his diary.

Two newsmen, John McCutcheon and Richard Henry Little, and a local newspaper called The Manila Freedom reported accounts which captured the imaginations of American and Filipino readers.

The Manila Freedom wrote this of del Pilar:[5] "It is said that in the battle against Major March's troops, Mr. Gregorio del Pilar, surrounded by the dead and the wounded falling by his side, fought a valiant defense, inspiring his troops by his example and, though gravely wounded, had stood atop the trench to animate then when a bullet pierced his heart and he fell among his comrades.

When the American troops advanced they found the body of the general on the same spot where he had fallen and the expression on his face was of a command or a supreme desire abruptly interrupted.

Our soldiers, pointing with their hands, warned del Pilar that the enemy was almost on top of us, but we could see nothing save an irregular movement in the cogongrass.

He wore a new khaki uniform with his campaign insignia, his silver spurs, his polished shoulder straps, his silk handkerchiefs, his rings on his fingers.

[17] Though Nable José's claim is based solely on an interview of her, there still remained a glaring lack of third-party sources to verify her story.

In an article published by the Boston Evening Transcript, McCutcheon details that Gregorio del Pilar and Dolores Nable José were set to be married around mid-November 1899.

[18] He also mentions the handkerchief found on del Pilar's body to be embroidered with Dolores' name, and that a number of the letters retrieved from his person were from her.

Additionally, Captain Isidro Wenceslao mentioned that Dolores was in del Pilar's thoughts during his last meeting with Aguinaldo.

Meanwhile, Isidro Wenceslao was part of the famed "Seven Musketeers of Pitpitan", a group of young men led by del Pilar that initially joined Maestrong Sebio's forces at Kakarong de Sili.