Ad Age looks at the tense marketing battle between Nike and official Olympic sponsor Adidas at this summer’s London Olympics:

Think Nike’s an Olympics sponsor? You wouldn’t be the only one making that mistake. It’s “Find Your Greatness” campaign manages to capture the Olympic spirit of competition without mentioning the Olympics, or words verboten in the UK like “medal,” “gold” and “games.”

As the Olympic Games began last week, Nike’s “Find Your Greatness” landed at No. 1 on the Viral Chart, with 4.5 million views (about 1.7 million paid). Compare that to Adidias, an Olympics sponsor, whose “Take the Stage” campaign, which arrived at No. 3 on the chart, with 2.9 million views, according to Visible Measures.

Overall, “Take the Stage” has had 5.7 million views (about 1.6 million paid) since it launched in April, so Nike has nearly caught up in just a week. Having firmly linked itself with London, many viewers believe that the brand is affiliated with the games. Last week, Ad Age reported that an online survey by Toluma Global Omnibus Survey found that of 1,034 US consumers, 37% identified Nike as an Olympic sponsor, compared to 24% for real sponsor Adidas.

If all this sounds familiar, well, it should. Nike used similar tactics to ambush the World Cup two years ago with its “Write the Future” campaign. It garnered 23.6 million views by the fourth day of the tournament and stole buzz from Adidas in a similar fashion. A YouGov study at the time found that Nike benefitted more than any other brand — including official sponsors like Adidas — from the World Cup tournament.

As an Olympic Partner, Adidas paid for exclusive marketing rights within the U.K. It spent £100 million on its Olympic marketing in the last four years, according to Katja Shreiber, Adidas senior corporate communication manager. That bill includes the sponsorship, outfitting athletes and advertising campaigns. Ms. Schreiber would not confirm the price tag of the sponsorship itself, which The New York Times reported was £40 million.

Nike could not be reached to discuss how much it spent on its Olympics effort, which includes this campaign and an apparel deal that allowed them to outfit the entire U.S. Olympic team with village wear, as well as the U.S. basketball, soccer, and track and field teams. Yet despite its success in ambushing the games, there has been some speculation that Nike will be an official sponsor of the 2016 Olympics in Rio. Adidas has already pulled out of sponsoring those games.