Valentin Cruz, who served as "Pangulo ng Sangguniang Bayan ng Pasig," was a gentleman-farmer, happily married to "Dorang" and with many friends. He led a comfortable life and was well-read just like his friend, Andres Bonifacio. Among his serious readings were the "French Revolution," "Noli me Tangere," "El Filibusterismo," "Florante at Laura," "Scientific Agriculture" and the Bible.

Agitated by these readings, Cabesang Valentin eventually accepted Bonifacio’s invitation to join the Katipunan, a secret society that aimed to unite the Filipinos and fight for Philippine independence. Cruz, by joining the patriotic society, had much to lose, but his sentiments were in sympathy with his compatriots who suffered from the tyrannical rule of a foreign power.

In the first Sunday of May 1896, an executive meeting of about 60 Katipuneros was held in Sitio Ugong in an unpopulated area north of Pasig. The Katipunan leaders from Manila, headed by Bonifacio, together with the delegation from Cavite, led by Emilio Aguinaldo, were in a convoy of five boats, going against the current of the Pasig River on sundown. It was a flotilla that increased as they were joined by other Katipuneros from Santa Ana, Mandaluyong, San Pedro de Makati, Pateros, Taguig and Pasig.

At around nine o’clock, the Katipuneros arrived at Sapang Nabas in Ugong. They were supposed to conduct their executive session at the eating-place owned by an old woman named Fausta. But there was constant drizzle and the dark clouds threatened to let down heavy rain. And since they expected their discussion to last until morning, they would be exposed to the heavy river traffic occasioned by the Antipolo fiesta. Moreover, they would risk detection by the Civil Guards who patrolled in boats.

So, Valentin Cruz, Katipunan leader of Pasig, volunteered to have their Asamblea Magna held in his house at the town proper. From Sapang Nabas, the Katipuneros traveled through rains in the dark through orchards and cane fields. Many fell into mud puddles, causing laughter and relieving tensions during the difficult trek. Arriving at their destination, the host quickly served them hot coffee and bread.

The house of Cruz was big, a great number filling the large reception hall at the top of the stairs. At eleven o’clock, Supremo Bonifacio conducted the meeting, sitting behind a table at the far end of the hall. On his left was Emilio Jacinto, Secretary, and on the right was Dr. Pio Valenzuela, the Prosecutor. The Triumvirate was joined by the host (Cruz), Aguinaldo, Candido Tirona, Santiago Alvarez, Benigno Santi, Aguedo Del Rosario, Pantaleon Torres, Enrique Pacheco and his son Cipriano, Nicomedes Carreon, Francisco Carreon, Ramon Bernardo, Alejandro Santiago, Apolonio de la Cruz, Gregorio Coronel, and Pio Santos, among others.

This was the meeting where Valenzuela argued that firearms were needed to hasten the overthrow of the Spanish regime – a motion that would be submitted to Dr. Jose Rizal in Dapitan for his approval.

After the meeting in Pasig, the visiting Katipuneros were able to return to their respective hometowns in safety, and the local Katipuneros thought they were safe for there were no untoward incidents, though in fact, the house of Cruz was a mere stone’s throw away from the Civil Guard station. However, a rumor cropped up that such a meeting did happen and it reached the colonial authorities. A Spanish officer was assigned to investigate the case, but he was killed on the job. The Spaniards thus arrested Cruz on suspicion of masterminding the killing. He was hung upside-down from the top of the bell tower of Pasig Church in full view of the parishioners. His head was dipped repeatedly in cold water until he lost consciousness.

Despite his torture, Cruz did not break down. Believing him dead, the other arrested Katipuneros pointed to Cruz as the person responsible for the killing. Seeing Cruz alive on the day following the torture, the squealers altered their testimony, pointing to an out-of-town person also named "Valentin Cruz" as the real culprit. With no evidence against him, and a substantial donation to the church by his mother, Cruz was released from prison.

After recovering from his torture, Cruz left his young wife and infant son in the care of his mother to continue his underground work for the Katipunan. The cover-story was that he needed to attend personally to the operation of his distant farms.

On the third week of July 1896, Andres and his brother Procopio Bonifacio, Valenzuela, Cruz and other Katipunan leaders from the provinces of Manila and Morong re-assembled at the ancient lighthouse located in Laguna de Bay near the mouth of the Pasig River that was a 20-minute boat ride from Napindan, Taguig. Valenzuela announced the result of his consultation trip to Dapitan with Rizal.

According to Valenzuela, Rizal commented, "So the seed grows," but cautioned the Katipunan to seek arms and the support of wealthy Filipinos like Antonio Luna. With the advice, the assembly became more resolved to proceed with the revolution. The lighthouse was their Rubicon.

There was no turning back. At the next event, the Katipuneros tore their cedulas, shouting, "Mabuhay ang Pilipinas! Mabuhay ang Katipunan!" It was August 23, 1896 at Pugad-Lawin.

On August 28, 1896, Valentin Cruz was in Balakbak Hills near Hagdang Bato in Mandaluyong where Bonifacio issued his formal war manifesto calling on all towns to rise in arms and attack Intramuros the next day at midnight. In that occasion, Cruz was promoted to General de Brigada at the young age of 31.

In early night of August 29, Pasig, simultaneously with Pateros, Mandaluyong and other adjacent towns, rose in freedom, with municipal halls and garrisons successfully attacked by the Katipuneros. It gave the Revolution a very auspicious start, and it is referred to in local history as "Nagsabado."