My dog always growling at my other dog how can I get them to stop fighting?

So I have a english springer spaniel who has been in my family for years and a couple of months ago we got a jack russel, at first everything was alright he didn't attack or growl just sat there and the springer(Alfie) always sniffed him. But now the russel(jack) starts to growl everytime Alfie comes near him and sometimes Alfie might growl back and start to fight each other. How can I get them to get Wong with each other and become friends?