, as painted by Nicodemus David Hufford III The retreat of Aguinaldo from
Bayambang, through the mountainous terrain began on November 13, 1899, after he had disbanded the regular Filipino army into guerrilla units. On November 23, Aguinaldo's party reached the pass, which provided a strategic bottleneck. It was to be protected by a rear guard under General
Gregorio del Pilar, who noticed the advantageous terrain of
Tirad Pass (
Pasong Tirad as it was locally called), and hunkered down to defend it while Aguinaldo escaped through the mountains. The hand-picked force of Filipinos, which was the remaining contingent of
Antonio Luna's army, constructed several sets of trenches and stone barricades on both shoulders of the pass, as well as on top of its height. Meanwhile, during early November, Major March had been given the task of pursuing Aguinaldo. By November 30, March and his men, in haste to catch the Philippine president, marched through
Candon,
Santo Tomas, La Union, and
Salcedo, Ilocos Sur. He and his men found out that Aguinaldo had passed through Salcedo five days previously, and that fueled the Americans' march to Concepcion (now named
Gregorio del Pilar), a town overlooked by the steep pass, which they reached by December 1. March had no clear idea of the size of Aguinaldo's rear guard, but he had calculated it to be no more than 150 men. ==Battle==