Joshua chapters 7 and 8 contain the story of the conquering of the city of Ai. Interestingly, it's one of the few defeats recorded, and then there is success.
I won't focus on Aachan's sin and the fact that one family in sin can derail the whole assembly. Instead, let's look at Joshua 8:1-2:
The Fall of Ai
8:1 And the Lord said to Joshua, “Do not fear and do not be dismayed. Take all the fighting men with you, and arise, go up to Ai. See, I have given into your hand the king of Ai, and his people, his city, and his land. 2 And you shall do to Ai and its king as you did to Jericho and its king. Only its spoil and its livestock you shall take as plunder for yourselves. Lay an ambush against the city, behind it.”
Notice how the Lord commands that all the men go to battle. If you look at chapter 7 you'll see that the people had originally tried to take the city with just a portion of the army:
3 And they returned to Joshua and said to him, “Do not have all the people go up, but let about two or three thousand men go up and attack Ai. Do not make the whole people toil up there, for they are few.” 4 So about 3,000 men went up there from the people. And they fled before the men of Ai,
I think what I'm seeing here is that I have a tendency to look at the assembly, the church, and say "Well, I'll take whoever will follow and go." That's ok in some cases, but when people are left behind simply out of an unwillingness to do the work, there's going to be trouble.
I know that we cannot always get unanimous agreement before we proceed with the actions, ministries, and plans of the church body, but we cannot simply leave out large chunks of the people. It's a recipe for failure.