You may have mastered every other skill a manager could possibly learn, but none of that will matter if you have not learnt to build and sustain your team effectively to begin with. Most tasks in modern business are carried out by teams, so the skill of ensuring that your team works to the best of its abilities is vital if you are to achieve your business aims.
John Eric Adair is a British academic who is a leadership theorist and author of more than forty books (translated into eighteen languages) on business, military and other leadership.