The feud between Taylor Swift and Katy Perry just went from bad to worse.

It doesn't look like the pop stars are looking to bury the hatchet anytime soon, and Katy recently addressed her beef with the "Bad Blood" singer on Monday, May 22, during an appearance on The Late Late Show Carpool Karaoke Primetime Special.

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"There's a situation. Honestly, it's really like she started it, and it's time for her [Taylor] to finish it," the "Bon Appétit" singer told host James Corden. "I tried to talk to her about it and she wouldn't speak to me. I do the right thing any time that it feels like a fumble. It was a full shutdown and then she writes a song about me, and I'm like, 'OK, cool, cool, cool. That's how you want to deal with it? Karma!'"

taylor swift katy perry

Of course the track Katy is referring to is the aforementioned hit "Bad Blood," which is allegedly about the pair's mutual dislike of each other. The song was released in 2014 on Taylor's 1989 album — and ever since, the two women have been frenemies. Scroll down for a complete timeline of this 21st century war!

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2013

Earlier in their careers, Taylor and Katy were friendly with each other. They often crossed paths at awards shows, and Katy even performed "Hot n Cold" at a Taylor Swift concert in 2010. Katy began dating Taylor's ex John Mayer in 2012, but the two women remained cordial.

It wasn't until 2013 when their relationship took a turn. Backup dancers from Taylor's Red World Tour — who had previously toured with Katy — were allegedly poached from her show for Katy's Prismatic World Tour.

2014

It's no secret that Taylor knows how to keep a grudge. The 27-year-old singer is not only famous for her voice, but for her killer songwriting abilities as well. While she won't explicitly name names in interviews she has no problem bearing the truth in her music.

During a 2014 Rolling Stone interview, the songstress revealed that her then unheard track "Bad Blood" wasn't about an ex-boyfriend — as the press might assume — but instead about a fellow female pop star.

katy taylor

"For years, I was never sure if we were friends or not," she said. "She would come up to me at awards shows and say something and walk away, and I would think 'Are we friends, or did she just give me the harshest insult of my life?'"

Taylor told the magazine, "She basically tried to sabotage an entire arena tour. She tried to hire a bunch of people out from under me."

Katy was quick to retaliate on Twitter.

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katy perry nicki minaj

2015

Two female superstars apparently weren't enough for a proper catfight because the next year "Anaconda" singer Nicki Minaj joined the battle. She tweeted in frustration about not receiving a nomination for the MTV Video Music Awards Video of the Year category, and Taylor took it personally because she did receive a nomination.

https://twitter.com/taylorswift13/status/623616796277506048

Katy then tweeted what many fans considered a response aimed at Taylor.

2016

At this point, the tension between the stars was common knowledge, and in a way, old news. But, Calvin Harris drudged up the ongoing fight after his bad breakup with Taylor. Her team revealed that Taylor was actually the songwriter on his hit "This Is What You Came For" and Calvin wanted to set the record straight. The DJ sounded off in a Twitter thread explaining that Taylor originally wrote the song under a pen name as a way to preserve her anonymity and was trying to flip the script post-breakup.

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He tweeted, "I know you're off tour and you need someone new to try and bury like Katy ETC but I'm not that guy, sorry. I won't allow it."

Not too subtle… the tweet has since been deleted, but by that time, the damage had already been done. Katy tweeted a response with a little help from the former Secretary of State.

2017

It might be four years since the first punch was thrown, but Katy is still in the ring. She surprised fans with a recent Nicki collaboration on the track "Swish Swish." The lyrics in the song seem to be a direct diss.

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"One thing to note is: You can't mistake kindness for weakness and don't come for me," she recently told Entertainment Weekly. "Anyone. Anyone. Anyone. Anyone. And that's not to any one persona and don't quote me that it is, because it's not. It's not about that. Honestly, when women come together and they decide to unite, this world is going to be a better place. Period end of story."

There's no denying the fact that the singers have bad blood, which makes us wonder if their feud will ever end. In the meantime, fans will at least get some great music out of it.