When Israel was final in the promised land, ready to take it as their own, God gave Joshua very strange instructions. He told Joshua to MAKE flint knives. I've never seen a flint knife but it does not sound like a surgical instrument. Especially not a field-made version. And worse, God told Joshua to circumcise all the men of Israel. No doubt they spent the next few days in a very vulnerable position!
Circumcision was a sign of God's covenant. It signified promise and ownership and holiness. All three of these ideas are closely related.
God has always sought a people that would follow him with all their hearts. This was a new group (with a few exceptions) and I believe he was giving some "101" lessons in people-of-God-hood. People of God are God's! They have his mark of ownership.
The next thing he asked them to do was conquer Jericho by another strange military tactic: marching quietly behind the ark of the covenant. Once again God's promise was to lead the way. His glory was to go first. They were to be God's people following God's way.
Do we show the mark of God's ownership in our lives? As a people? As a church? Do we let God's glory and promise lead us? Do our methods leave no doubt as to who won the battle?