When I commanded in the Army, I learned a huge lesson in momentum. When you put a whole unit in motion, carrying out a plan, it's extremely difficult to redirect them. Even something as simple as a change in direction is hard to do.
That may be the best test of leadership: Your ability to get your team to change directions quickly. When you need to do that, here's what you're up against.
1. People may not know what to do. They know to do what they're doing now; if you change things up will they know their role then? The Army and sports both use drills, which is practicing a fundamental task over and over until the whole team can do it without thought. Then all that's need is for a leader to call for that action, and the whole team knows its part. Not many other organizations have coached their people that well.
2. People may not understand why. You spent some time telling them why the plan you decided to execute is good; why do you need to change it now? Sometimes you have time to explain, sometimes you don't.
2. People may not buy in. These days we're all about making the team part of the decision process, of giving them ownership. The down side to that is they won't want to change without the same chance to mull their way through and buy in.
So how do you get people who don't know what to do, or why to it, or who don't buy into the need to do it, to turn together and head in a new direction? It all comes down to trust: trust that you know what you're doing, trust that you know what they should be doing, trust that you have their best interest in mind, trust that if you'd had the time you would have involved them in the decision. In essence, to follow you at that moment is a clear statement that they believe you know best.
Bottom line: If your team doesn't trust you, they won't follow you. That's why a quick change of direction is a great test of your effectiveness as a leader.