“Elisha the prophet called.” Years before this, Elijah the prophet had been instructed to anoint Jehu as king of Israel (1 Kgs 19:16). It was accomplished through his disciple and agent, Elisha,
“Tuck your cloak under your belt.” The literal Hebrew is “belt up your loins.” This refers to the custom of a man tying up his long clothing so he could move more quickly. See commentary on 2 Kings 4:29.
“go to Ramoth-gilead.” The combined armies of Israel and Judah were not able to conquer Ramoth-gilead, but they were fighting there, which is why Jehu, a commander in the army of Israel, was there. Joram was the current king of Israel, but the fighting over Ramoth-gilead had been on and off for years. A previous king, Ahab, had been mortally wounded there (1 Kings 22:35)