When Chris Broderick and Shawn Drover became frustrated with the direction their music with Megadeth had taken on 2013's Super Collider, they took matters into their own hands by leaving one of heavy metal's Big 4. But just because they planned to stick together musically didn't guarantee that their resume would instantly result in big tours or gratification.

And they knew that.

Displaying the will to work from the ground up despite their pedigree, the duo teamed with Shadows Fall guitarist (turned bassist) Matt Bachand and vocalist Henry Derek, who had worked with Slipknot (now Vimic) drummer Joey Jordison in Scar The Martyr.

Act Of Defiance was born.

But after 2015 debut Birth and the Burial, the group's road show included Austin, not San Antonio. That finally changed Thursday night as AOD made its live Alamo City debut by headlining The Rock Box behind sophomore effort Old Scars, New Wounds via Metal Blade Records with Shattered Sun and locals Killstorm.

On the same night Pop Evil headlined the Aztec Theatre with Palaye Royale and Black Map, Act Of Defiance found itself in a peculiar situation: four established band members, whose group would be an ideal candidate for a secondary-stage slot at the soon-to-be announced sixth annual River City Rockfest, were about to perform before a scant 50 metalheads.

Those not on hand missed an hour-long dose of supreme heaviness. Songs such as "M.I.A.," "Belial," "Overexposure," "Lullaby of Vengeance" and "Dead Stare" (Facebook Live footage of the latter two here) exhibited Act Of Defiance's penchant for no-holds-barred riffs, drumbeats and Derek's in-your-face vocals (see setlist in slideshow below). Derek nearly made it through the entire performance without the audience knowing it was his birthday until Broderick spilled the beans prior to finale "Throwback" (ATM footage below). At one point, he curiously asked the fans who among them had the new album, only to segue into debut-disc track "Legion of Lies."

Broderick and Drover spoke with me separately on the same day in 2015 just prior to Act Of Defiance's first album being dropped, discussing how the band came about. Following Thursday's performance, as the quartet graciously met with fans, signed autographs and posed for photos, Drover lamented the turnout but also declared, "We need to go out and support somebody." Act Of Defiance will be doing just that when it opens for Armored Saint in July and August. However, no Texas dates have been scheduled.

Bachand, who lent his death-metal backup vocals to Stryper's new single "Take it to the Cross", shared with Alamo True Metal concerning the current tour: "It was either stay home or go out on the road and do this tour."

Although Act Of Defiance left out personal new thrashing favorite "Molten Core," the band's performance demonstrated that AOD is more than just getting started. The members' respective histories may have laid the groundwork for Act Of Defiance's birth.

But there's potentially a few years of music remaining before its burial takes effect.