The answer is: Ai

Joshua 7:3 - If Joshua had prayed to God he would have known not to send the men into battle

The story of the Israelites' defeat at Ai carries powerful lessons about humility and reliance on spiritual wisdom. It's fascinating how a moment of oversight—like forgetting to communicate with a higher power—can lead to significant consequences. Ai, a small town compared to Jericho, symbolizes this reality well. The Israelites had just conquered Jericho, a formidable fortress. One might think their momentum would carry them through any challenge. It’s a reminder that success can make us overconfident, prompting us to skip over essential spiritual practices like prayer.

When we examine Joshua’s actions, we note how critical communication with God was for strategic decision-making. Following that defeat at Ai, Joshua fell on his face before God and sought guidance, showing that he wasn’t above making mistakes and learning from them. Interestingly, in the broader context of battle narratives, reliance on divine wisdom is echoed throughout Scripture—one memorable example is David, who consistently sought God's counsel before facing his enemies, securing many victories.

This event also provides additional food for thought—it posits a counter-narrative to the triumphalist mindset often seen in conquerors. Aaron's dialogue around the sin that led to the defeat highlights the theme of collective responsibility. This is a corner-stone in many stories of the Israelites—ultimate victory didn’t solely rely on wielding swords but also on the posture of heart and the acknowledgment of divine instruction.