John Gill Commentary 2 Kings 6:24

"And it came to pass after this, that Benhadad king of Syria gathered all his host, and went up, and besieged Samaria." — 2 Kings 6:24 (ASV)

And it came to pass after this, that Benhadad king of Syria
gathered all his host
Still retaining a grudge and enmity against Israel, and not at all softened by the kind and humane treatment his forces had met with, when in the hands of Israel; and finding he could do nothing in a secret way, by ambush, mustered all his forces together, to try what he could by open war:

and went up, and besieged Samaria ;
Jehoram king of Israel not being able to stop him till he came to his capital, which he laid close siege to.