The Slaughter of the Ammonites (1 Samuel, Chapter 11)

David Punishing the Ammonites. By Gustave Dore, created in the 1800s

Strange things start brewing when an Ammonite named Nahash meets up with the elders of Judah.  The elders offer a peace treaty and an alliance (i.e. a covenant), and Nahash essentially says, "We can have peace if you allow me to pluck out each of your right eyes."

The elders are taken aback, and said, "Hm, give us seven days.  If no one wants to save us, then we'll come to you."

The elders go back to the city and tell the inhabitants of their plight, to which they all cry.

The elders then run to King Saul, who gets angry (actually, God gets angry and that's why Saul gets angry) and thus Saul's first task as king will be dealing with the Ammonites.

Saul basically rounded up 30,000 Israelites from Judah and then laid waste to 300,000 Ammonites, "slaying the Ammonites until the heat of the day."  The Ammonites survivors were so few and scattered about that no two were left together.

Afterward, Saul enters Israel (where the Ammonites were), and renews the kingdom in Gilgal.  A celebration of the new king of Israel then ensued, with God knows how many sacrifices, and all the men had fun.  Presumably, the women had to clean up after them.  Wow, not much changed after so many thousands of years!