The backswing is one of the crucial movements in the golf swing. It starts with the takeaway and ends at the top of the backswing. There is no static top though as a good golf swing is a fluid movement of the body and the backswing and the downswing which is the next movement in the golf swing tend to merge into each other. There is no separation between the backswing and the downswing in a strict sense. In the case of good players, one may notice that part of the downswing is activated even as the backswing is being completed. This is not to say that the backswing can be shortened or abbreviated or that it is all right not to finish thebackswing. Completion of the backswing and reaching the top position is vital for achieving a good downswing and the resultant impact. It only means that fluidity and smoothness is essential for a good golf swing and therefore no artificial separation between different parts of the golf swing should be made.
The back swing is apparently an easy movement in the sense that it is natural for the body and the hands to move backwards when attempting to hit something. However, most swing actions in golf cannot be said natural in the sense that they come naturally to the body. You need to learn the swing action and then try to do it in a natural way and not in a forced way. It is like educating your muscles to do something which they are ignorant of even though they have the capability for it.
The backswing begins with a gentle imperceptible initiating movement called the takeaway. The movement starts from the ground up. The lower part of the legs gets into the action first, followed by the upper legs and the body. The shoulders don’t turn before the hips do and the hands remain passive even though the shoulders have started turning. Being passive does not mean they stay lifeless. They remain alert and primed for action but keep quiet until the shoulders have transferred the movement to them. This sequential movement of different parts of the body from the legs to the hips, to the trunk and the shoulders and finally the arms and the hands is actually one smooth movement without any physical or temporal separation. When the hands and the club get to the top the backswing can be said to be complete even though it actually does not end abruptly but quietly merges into the downswing.