Final answer:
Jehoshaphat joined with Ahaziah to build ships for trade and maritime expansion.
Step-by-step explanation:
In the Bible, King Jehoshaphat of Judah joined forces with King Ahaziah of Israel to build ships in order to sail to Tarshish. However, their joint venture ended in disaster as the ships were destroyed before they could set sail.
This event is recorded in 2 Chronicles 20:35-37. The primary reason for their alliance was likely for the purpose of trade and expanding their maritime capabilities.