2 Chronicles 15: Asa

In those days it was not safe to travel about, for all the inhabitants of the lands were in great turmoil. 
One nation was being crushed by another and one city by another, because God was troubling them with every kind of distress. 
But as for you, be strong and do not give up, for your work will be rewarded.” 
When Asa heard these words and the prophecy of Azariah son of Oded the prophet, he took courage. He removed the detestable idols from the whole land of Judah and Benjamin and from the towns he had captured in the hills of Ephraim. He repaired the altar of the LORD that was in front of the portico of the LORD ’s temple. 
Then he assembled all Judah and Benjamin and the people from Ephraim, Manasseh and Simeon who had settled among them, for large numbers had come over to him from Israel when they saw that the LORD his God was with him. - 2 Chron. 15:5-9 NIV

At first glance, it would seem that Israel should have been the most successful of the two nations formed when the kingdoms of Rehoboam and Jeroboam split.  Judah consisted of only two tribes, Judah and Benjamin plus the Levites.  The rest of the tribes split off under the leadership of Jeroboam.  After a rocky start under Rehoboam when he refused to follow the Lord God, he came to his senses and Judah began to prosper.  That prosperity continued under Rehoboam's son, Abijah, and his son, Asa.  So much so that large numbers of the tribes that represented Israel moved into Judah's territory when they saw that God was with them. 

Sometimes, all it takes is standing up for God and against evil to turn the tide of nations.  Israel would meet it's demise more than a hundred years before the fall of Jerusalem, by which time, Judah had forsaken God as well.  It may seem foolhardy to follow after God when nations and cities are being crushed by one another, but it was God that was bringing about the distress and in that instance, the only solution is to fall on the Rock that is Higher.  Any other response will result in crushing defeat.