ABBA’s singles did well whatever time of year they were released, but the Swedish superstars thrived in summer, and August 9 is an especially successful day in their history. On that date in 1980, they achieved the eighth of their nine UK No.1s with “The Winner Takes It All,” and exactly five years before that, the group entered the Billboard Hot 100 with “SOS.”

“The Winner Takes It All” was widely hailed by fans as the release that took ABBA to new heights of pop sophistication. It was also perhaps the most poignant lyric ever written by Björn Ulvaeus and Benny Andersson, as it described the disintegration of a relationship, not only as Björn and Agnetha’s marriage reached its end, but with Benny and Frida now having problems of their own.

This first single from the new Super Trouper album featured an impassioned lead vocal by Agnetha, who had to perform to camera for the video just ten days after her divorce from Björn became final. Whether their millions of admirers were aware of that or not, they loved the single. “The Winner Takes It All” debuted on the British chart at No.9 before starting its two-week run at the top. In November, when the Super Trouper LP arrived, that spent a majestic nine weeks at the UK summit.

Back in 1975, ABBA were chiefly known in America, as in many countries, for their Eurovision winner of the year before, “Waterloo.” Only “Honey Honey” had charted since, and that peaked at No.27. But “SOS” won significant airplay support from American radio stations and debuted on the Hot 100 several weeks before it charted in some other territories, albeit at a modest No.89.

A week later, things didn’t look good. The song lost its “bullet,” the Billboard symbol that denoted a strong increase in weekly sales, as it struggled to No.84. Sure enough, a week later, it was gone from the Hot 100. Then something remarkable and unusual happened. “SOS” re-entered the countdown on September 6 at an even more tentative No.99, before climbing ten places. Then it again looked doomed, when it lost its bullet a second time, inching to No.86.

But somehow, the single kept going, radio stations kept adding it to their playlists and record buyers responded. It regained its momentum with a jump to No.76 and then really took off, vaulting to No.53, 40, 24 and on into the Top 20. “SOS” peaked at No.15 in the States that November.