Sienna Miller had nothing but good things to say recently about her American Sniper co-star Bradley Cooper.

According to the Boston Globe, the 32-year-old actress gushed over Cooper for his dedication to his work, calling him a “phenomenal actor” who was fearless in showing his character’s emotions.

“He never broke character, so I really got to know Chris Kyle before Bradley Cooper,” said Miller, referring to Cooper’s character in the film.

The British actress, who portrays Chris Kyle’s wife Tara in the film, took a few moments to speak on the nature of war. Over the summer, she volunteered at a Syrian refugee camp in Lebanon and said that between her charity efforts and working on American Sniper, she has a newfound respect for all those who put their lives on the line to defend their country.

The Clint Eastwood-directed American Sniper will be released in theaters on January 6, 2015.

Take Aim: Our Review Of Clint Eastwood's 'American Sniper' Starring Bradley Cooper http://t.co/Zh6pwqsg9W pic.twitter.com/LlrZHnpmzk

— ThePlaylist (@ThePlaylist) November 12, 2014

Is this Sienna Miller's hottest red carpet look? We think it may be… @Burberry http://t.co/zg3pmh10ob pic.twitter.com/5XyooCek37

— InStyle (@instyle_UK) December 1, 2014

Meanwhile, the first full-length trailer for Miller’s film Unfinished Business, in which she stars alongside Vince Vaughn, was released on Nov. 27.

The Ken Scott-directed film follows the trials of Vaughn‘s character, who goes from being an employee of Sienna Miller’s company to becoming one of her greatest competitors for a major client, despite the fact he is just starting his company and doesn’t have the resources of his former employer.

Take a trip down memory lane with #Foxcatcher star Sienna Miller's style evolution: http://t.co/RuY40COa4Z pic.twitter.com/GMplTBzQK7

— StyleBistro (@StyleBistro) November 14, 2014

The David v. Goliath-themed movie also stars James Marsden, Dave Franco, June Diane Raphael and Nick Frost.

Unfinished Business is scheduled to be released in theaters on March 6, 2015.