Charlie Daniels' 40th anniversary Volunteer Jam on Wednesday (Aug. 12) had plenty of surprises sprinkled throughout the evening, including appearances by Blackberry Smoke and Lynyrd Skynyrd. Another shock that got the crowd cheering was an appearance by Eric Church during the Charlie Daniels Band's set.

As Daniels and crew readied "In America," the lead single from their 1980 record, Full Moon, Church appeared onstage, much to the delight of the sold-out audience. Daniels backed Church on electric guitar and let his fellow North Carolina native plug in his acoustic axe and take the lead.

Church himself was all smiles standing next to Daniels. He delivered a rousing rendition of the song, shaking his fist and proclaiming the strength of America. At the end of "In America," Daniels extended his hand to the singer, exclaiming, "Eric Church, everyone!" before enveloping him in a bear hug. Press play on the video above to watch their performance.

While Church's appearance was a huge surprise for the audience on Wednesday night, Daniels' biggest Volunteer Jam-related surprise came many years ago.

"I was standing onstage one night, and I looked, and out of the corner of my eye, I saw my all-time hero Roy Acuff," Daniels recalled to The Boot and other media outlets before the event. "Had no idea he was there. And he was standing over there, grinnin' like an opossum.

"He was such a nice, warm-hearted man. He had come between shows at the Grand Ole Opry ... just because that was the kind of guy he was," Daniels continues. "He got such a big charge out of it. So I brought him out. The crowd went nuts; they just loved him. He came out and did a couple songs."

Daniels adds, "Yeah, I've had people show up that I didn't know was gonna be here. This is Nashville, after all."

The 40th anniversary Volunteer Jam, benefiting U.S. military and veterans through the Journey Home Project, featured Ted NugentTrace AdkinsAlabamaTerri ClarkBilly Ray CyrusColt Ford, the Grascals, the Kentucky HeadhuntersTracy Lawrence, the Oak Ridge Boys, Ryan Weaver, Wynonna JuddCraig Morgan, Lee Roy ParnellBilly Dean, Michael W. Smith, Travis TrittPhil VassarMontgomery Gentry and more, in addition to surprises guests Church, Blackberry Smoke, Lynyrd Skynyrd and Jamey Johnson.

See Pictures From the 40th Anniversary Volunteer Jam