Brotherhood of Man are a British pop group who achieved success in the 1970s. They won the 1976 Eurovision Song Contest with "Save Your Kisses for Me". Created in 1969 by songwriter and record producer Tony Hiller, Brotherhood of Man was initially an umbrella title for a frequently-changing line-up of session singers. Early on, they scored a worldwide hit with the song "United We Stand".

Brotherhood of Man were formed by record producer/composer Tony Hiller in 1969, and originally featured his co-writer John Goodison with Tony Burrows, Roger Greenaway, Sue Glover and Sunny Leslie. Greenaway was also a songwriter and had co-written hits such as "Something's Gotten Hold of My Heart" and "Melting Pot". Burrows was a well-known session singer, performing in various line-ups on hit singles such as the No.1 hit "Love Grows (Where My Rosemary Goes)" by Edison Lighthouse. The two female members, Glover and Leslie were an act in their own right, releasing singles as Sue and Sunny.  The group came together in 1969 and began recording some songs with Hiller. Their first single "Love One Another" failed to chart, but the follow-up "United We Stand" (released in January 1970) was a worldwide hit. "United We Stand" was heavily played on British radio, and broke into the American market. The single became a Top 20 hit in the UK, Canada, and US. The song has since been used as the closing theme for television's Brady Bunch Hour and as an anthem for various causes. Burrows left the group soon after and as a four-piece, The Brotherhood of Man followed "United We Stand" with another hit, "Where Are You Going to My Love". The song charted in the UK, Canada, and US and has since been covered by Olivia Newton-John and The Osmonds among others. A debut album United We Stand followed soon after.  Over the next two years, the group continued in varied line-ups. Goodison left the group at the beginning of 1971 and was replaced by American singer Hal Atkinson, Greenaway left soon after and was replaced by Russell Stone. They had one more minor hit in the US (1971's "Reach Out Your Hand"), but experienced no further success in the UK and split after being dropped by their record company.

Answer the following question by taking a quote from the article: why did they leave?