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Sorry to disagree with the OP's premise but the Bible indeed describes the Battle of Mount Zemaraim as a miraculous victory for Judah. Unfortunately the enemy in this case was Israel. Judah's army was outnumbered 2-1 in terms of troops and the enemy king had trapped Judah's army in a ambush, effectively surrounding it.
2 Chronicles 13 then describes God's miraculous intervention in response to Judah's prayers and priestly trumpet calls:
Jeroboam (of Israel) had sent an ambush around to come on them from behind; thus his troops were in front of Judah, and the ambush was behind them. 14 When Judah turned, the battle was in front of them and behind them. They cried out to the Lord, and the priests blew the trumpets. 15 Then the people of Judah raised the battle shout. And when the people of Judah shouted, God defeated Jeroboam and all Israel before Abijah and Judah. 16 The Israelites fled before Judah, and God gave them into their hands. 17 Abijah and his army defeated them with great slaughter; five hundred thousand picked men of Israel fell slain.
Biblical numbers of soldiers and casualties are highly controversial, and may be taken with a grain of salt. However, the answer to the OP's question is the Battle of Mount Zemaraim. God's decisive response to prayer in the midst of a hopeless military situation is definitely miraculous.