Why Leeds United and Manchester United are sworn enemies?

The hatred between Manchester United and Leeds is called "Rose Confrontation" in Britain, because its root comes from the famous "wars of the roses" between Lancashire and Yorkshire in the 5th century. The two families fought to the death for the British throne. The "bloodiest battle in British history" in this war took place near Leeds. At that time, the color of the jersey directly reflected which family the club belonged to. Leeds is the white rose of Yorkshire, while Manchester United is the red rose of Lancashire. The hatred evolved from wars of the roses has nothing to do with football, but it basically covers all sports fields in Britain at that time. You can see roses, red or white on the signs of many English clubs. During the British industrial revolution, the British economy developed rapidly. Leeds focuses on wool industry, while Manchester focuses on cotton industry. Later, the price of cotton cloth became cheaper and cheaper, which completely occupied the wool market and made the textile workers go to Manchester. Later, Leeds built a "first-class Leeds City Hall", and Manchester also built a "first-class Manchester City Hall" as a counterattack. First-class listening to Manchester City Hall (different levels, different levels of buildings, see Wiki for details) In the 1970s, at the peak of football hooliganism in Britain, Red Army, a radical fan organization of Manchester United, and Service Crew, a radical fan organization of Leeds, created a series of super violent conflicts. Many fans were injured in the confrontation between the two organizations. Even today (before Leeds was demoted in 2003), the British police will send the highest-level police force to maintain the safety of the stadium. You should remember that in the UEFA Cup in 2000, two Leeds fans were stabbed to death by galata in the post-match conflict between Istanbul and Sylar. Afterwards, many Manchester United fans were very sad and personally went to the Elam Road Stadium to express their condolences. There are even reports that there are photos of Manchester United fans and Leeds fans hugging and crying. However, when the two teams returned to the stadium, everything returned to a deep state of hostility. In retaliation for the unbearable slogans and songs of Leeds fans after the Munich air crash, some radical Manchester United fans hung up the slogans of "mufc Istanbul Red Man" and "Galatasaray Red Man" after the tragedy in 2000. Like Liverpool, their respective air crashes have also sublimated the hostile relationship between the two clubs. 200 1, Leeds United, known as the "Young Guards", rushed into the semi-finals of the Champions League, and then the price of all this was the financial crisis, and they had to sell their stars, and finally they were relegated in the 2003-04 season. Speaking of Leeds United and Manchester United, I have to mention the hero of Elland Road, alan smith, who kissed the badge of Leeds United passionately and vowed never to leave even if Leeds were relegated. Alan smith once said in an interview that he would never join Manchester United, even after his demotion in 2004, which angered all Leeds fans and called him Judas. On the other hand, Manchester United fans warmly welcomed him to Old Trafford, admiring his courage to join his sworn enemy and quickly becoming the favorite of Manchester United fans. Although the two teams have never met since February 2004, the hatred between the fans of the two teams continues, which strongly proves that the fans of both teams now sing opponents' songs from time to time when their teams compete with other teams.