The three reasons of Houston's retreat includes-
(i)poorly trained army,
(ii) lack of military equipment and
(iii) arrival of Santa Anna's Mexican army.
Step-by-step explanation:
After the defeat of Texan army, the new general of Texan Sam Houston adopted a series of retreats to fight the Mexican army. Houston decided to retreat because he had a poorly trained military with little amount of ration and less experience and he wanted to get more time to train this army against the fierce Mexican army of Santa Anna.
To fight with the Santa Anna army Houston strategically opted for retreats and gained more time to prepare his army