On the night of 21 November the combined Armies of El Salvador and Honduras, known as the "Ejército Protector de la Paz" under the supreme command of Malespín, with Guardiola as second and José Trinidad Muñoz as third in command, set up camp at the Barranca de San Antonio gorge, and at 8 p.m. on 26 November they reached León and set up camp in the outskirts of the city.

Disorder ensued and the Honduran troops began to withdraw, but Malespín convinced them to stay in combat, not before Commander Manuel Quijano y García and 64 dragoons had already deserted.

Initially, about 400 Matagalpa archers enlisted in the defense of León against the invading army, but due to the mistreatment they received from the liberal "Grand Marshal" and the breaking of the liberal-conservative alliance, they joined the occupying forces.

[4] In an attempt to avoid war, when the invading forces reached Barranca de San Antonio on 21 November, peace negotiations began at the hacienda "Satoca" located southeast of Somotillo.

The Nicaraguan delegates were Canon Desiderio Cortés and Anselmo Alarcón, representing León, José Francisco del Montenegro, Granada and Juan Ruiz, Rivas.

[10] Montenegro and Ruiz were the ambassadors sent by Granada and Rivas to Malespín, with the result of the creation of a provisional government in charge of Silvestre Selva based in Masaya, without the consent of León under siege.

[11] A shipment of weapons for the Leonese, on a ship docked at the port of El Realejo in the department of Chinandega, accidentally fell into the hands of the invading forces (Malespin actually obtained information from an Englishman named Manning, an agent of Selva's government).

[12] With the newly found equipment, on 22 January 1845, Salvadoran commanders Manuel Quijano y García and Ramón Belloso ordered the Matagalpa archers to set fire to the straw houses of Sutiava and occupied it, allowing the advance towards León.

He also allowed his troops to abuse the civilian population by raping women and stealing religious treasures from churches and houses as payment for "war expenses".

The Vice President of El Salvador, Joaquín Eufrasio Guzmán, conducted a coup against Malespin on 2 February 1845 and was joined by the greater part of the inhabitants of the capital, and a portion of the general's small army.

In the Peace Treaty it stated that El Salvador and Honduras were to pay expenses for the lootings and massacres, as well as return all stolen weaponry, the resegaition of José Trinidad Muñoz to the governorship of León, and the extradition of Joaquín Rivera, Maximo Orellana, Miguel Álvarez Castro, José Trinidad Cabañas, Gerardo Barrios, Diego Vigil y Cocaña and Ramon Vijil.

[4] Because of the murders of Dionisio Urcuyo y Crespín and Desiderio Cortés, Bishop Jorge de Viteri y Ungo excommunicated Malespin on 23 February in the Cathedral of San Salvador.