It's one of the most bitter rivalries in football - and this fascinating video shot at Elland Road shows the reality of Leeds United v Manchester United fixtures in the 1970s.
The Red Devils arrived to play Jimmy Armfield's Leeds side in their First Division clash on October 11, 1975.
This footage from the day shows fans arriving by train and coach from the other side of the Pennines, and a large police presence was there to meet them.
Mounted officers and dog handlers can be seen running at groups of teenage fans, and several young men are detained and searched during the tense build-up.
Flared trousers, platform shoes and long hair are on show from both sets of fans.
Leeds lost the game 1-2 after a brace of goals from Northern Ireland international Sammy McIlroy. Armfield faced criticism for replacing striker Duncan McKenzie with teenage rookie Carl Harris with the Whites 0-2 down, although they did manage to pull a goal back through Allan Clarke.
Tommy Docherty's Manchester United were top of the table at the time, although Leeds were missing Peter Lorimer, Gordon McQueen and goalkeeper David Harvey on the day.