José Mariano Hernández Martínez was born on 28 July 1786 in Suchitoto, San Salvador, then a part of New Spain.

[1] From 1822 to 1823, Hernández was a Salvadoran soldier and fought against Mexican forces during its conquest of El Salvador.

[1] On 24 April 1859, Hernández was assaulted and seriously injured by Tubircio Santa Cruz in an attack on his home.

[2] During the War of 1863, Hernández came out of military retirement and commanded forces for President Gerardo Barrios at the Battle of Coatepeque.

After the battle, Barrios ordered Hernández's arrest and he fled to Guatemala to support Francisco Dueñas' invading army.