After the four failed expeditions on Junkceylon, Bodawpaya gave up on wars with Siam, and now looked to the small states to the west. The first target was Manipur, which had regained independence from Burma since 1782. In February 1814, he sent an expedition force to place his nominee Marjit Singh to the Manipuri throne. The Manipuri army was defeated after heavy fighting, and its raja Chourjit Singh fled into Cachar. However, Marjit Singh revolted after Bodawpaya died in June 1819. The new king Bagyidaw sent an expedition force of 25,000  in October 1819. Gen. Maha Bandula reconquered Manipur but the raja escaped to neighbouring Cachar. In November 1820, the fallen raja's forces laid siege to the Burmese garrison at Imphal, and withdrew only when Burmese reinforcements were approaching. Nonetheless, the raja continued to raid Manipur with British support using his bases from Cachar and Jaintia, which had been declared as British protectorates, to the First Anglo-Burmese War in 1824.
Question: How many months was it between the raja escaping to Cachar after Bagyidaw's invasion force and the raja's forces laying siege to the Burmese garrison at Imphal?
Answer: 13