Answer based on context:

In April 1520, Cortés was told by Moctezuma, that a much larger party of Spanish troops, consisting of nineteen ships and fourteen hundred soldiers under the command of Pánfilo de Narváez, had arrived. Pánfilo de Narváez had been sent by Governor Velázquez from Cuba to kill or capture Cortés, who had defied Velazquez's orders. :281 Leaving his "least reliable soldiers" under the command of the headstrong Pedro de Alvarado to guard Moctezuma, Cortés set out against De Narváez, who had advanced onto Cempoala. Cortés surprised his antagonist with a night attack, during which his men wounded Narváez in the eye and took him prisoner. After Cortés permitted the defeated soldiers to settle in the country, they "passed with more or less willingness to Cortés' side." Hernán Cortés gained their support when he "promised to make them rich and give them commands ." Cortes then made a rapid return to Tenochtitlan, to relieve the besieged Alvarado and the other invaders.:282-84 Cortés led his combined forces on an arduous trek back over the Sierra Madre Oriental, returning to Mexico on St. John's Day June 1520, with 1300 soldiers and 96 horses, plus 2000 Tlaxcalan warriors.:284

How many months after Cortes was told by Moctezuma that a larger party of Spanish troops had arrived did Cortes led his combined forces back to Mexico?
2