Katy Perry Transforms Into a Marine for New Music Video

By Alison Schwartz

03/22/2012 at 01:05 PM EDT

In her latest music video, Katy Perry is laying off the sweets. No cotton candy and no cupcake bra.

Instead, she cuts her hair, wraps down her breasts and joins the Marine Corps.

The video for Perry's power-pop breakup anthem "Part of Me" – a song she says is not about her ex-husband Russell Brand, from whom she split in December 2011 – shows off her sugar-free, tough-tom boy side.

PHOTOS: Katy & Russell's Most Romantic Moments

"This is one of the most aggressive videos I've ever done," Perry, 27, tells MTV, which premiered her video (watch it above) Wednesday. "It's an affirmation of strength, so I wanted to go the strongest route I ever could."

After the woman she plays in the video breaks up with her lying, cheating boyfriend ("I'm done," she proclaims), she sees a flier: "All women are created equal, then some become marines," it says, all-caps.

So, like Rihanna in Battleship and Demi Moore in G.I. Jane – not to forget Goldie Hawn in Private Benjamin – Perry slips into fatigues alongside real-life, equally muddy Marines.

"For three days, I was a wannabe Marine," she says of the filming process, "which was so difficult."

RELATED: Katy Perry Finds Puppy Love in Paris