Thanks for contacting World Warfare Support.
There are two possible reasons as to why you cannot go back to a battlefield.
First, if you have chosen to "Surrender and Leave", you cannot go back to this battlefield. But you can join a new battlefield if there is a new one.
Second, if you are unable to return to a battle after a long time and haven't chosen to "Surrender and Leave", please report this to us via "Contact Us".