How do I call back my APC from marching to war ?

This will depend on what you are doing, not all marches can be recalled.

In the world view tap on the march in the list that shows on the upper left when the APC is out. The list is the entries with the wheel and progress bar that show what each APC is doing (if thy are in action). Tap on the required APC to locate it and if there is the option to recall it is will be shown. If you do have the option then you will need to have a recall item in your inventory, or pay for one using 50 diamonds to make the march recall.