I'm new.  How do I recall troops in route without spending 300 diamonds that I don't have?

Sir..There is an instant recall boost that you can recieve as part of a "special" Diamond purchase...But if you do not buy Diamonds..then to purchase instant recall does cost 300 Diamonds,,,Now you can win Diamonds as part of event rewards that you could save to be able to but the recall..Other that that Sir,,you will just have to be sure you want to finish the hit before you send them off