Steven Spielberg’s most commercially successful series in recent years has been TNT’s sci-fi entry “Falling Skies.” The popcorn drama, starring Noah Wyle as a history professor who winds up leading a resistance operation after an alien invasion, has blossomed into a big-tent hit for TNT, opening its third season on June 9 to strong numbers. The series also has a lucrative off-network licensing pact with Amazon Prime.

Falling Skies” has been the little creature feature that could for Team Spielberg. The series, co-produced with TNT, was birthed in 2010, around the same time DreamWorks TV was helping to shepherd time-travel drama “Terra Nova” onto Fox. “Terra Nova” had the bigger budget (and no fewer than 11 exec producers), but the ambitious production traveled a rocky road from the start. Nor was it a purely homegrown property for Spielberg.

Spielberg had long nursed an idea for a drama series in which a widowed father fights to keep his three sons alive against an invading force that targets children to work as slaves controlled by telepathy and gruesome harnesses that grow on their backs. Instead of tapping into the established pool of sci-fi specialists, Amblin TV toppers Justin Falvey and Darryl Frank went into left field for the writer to execute the boss’s vision: Robert Rodat, who earned an Oscar nom for penning Spielberg’s 1998 war epic “Saving Private Ryan.”

Rodat sealed the deal when he mentioned without prompting to Falvey and Frank the same two movies as inspiration for the series as Spielberg had cited in their initial brainstorming sessions. One of them was a fairly obscure 1959 German pic “Die Brucke” (“The Bridge”), about a group of child soldiers tasked with guarding a bridge. The other was Alfonso Cuaron’s futuristic 2006 film “Children of Men.”

“We never saw (‘Falling Skies’) as a sci-fi show. We saw it more as a war film,” Rodat says. “It was a really good sign that we both independently brought up these two films to Darryl and Justin.”

Rodat and Spielberg worked out the basic architecture of the series. Rodat based much of the family dynamic on his own three sons.

“The most striking thing about the process was that even though Steven had a full plate of feature work, he was deeply involved in the nuts and bolts of (‘Falling Skies’),” Rodat says. “He weighed in on big issues and small issues — the casting, the effects, the creature design, the costumes and the weaponry. I got the sense that he found this show to be a lot fun.”

Spielberg credits the trail blazed by the Syfy remake of Battlestar Galactica for convincing him that champagne vfx could be pulled off on a beer budget and weekly series timetable.

“That was the first time on a television show that I saw the promise of what low-res, creatively astute special effects could do … and I was really impressed,” he said. “They were making that show (on) a shoestring, and the effects looked like a big-budget tentpole movie.”

“Falling Skies” uses plenty of CG tricks — puppets, guys in rubber suits and a symphony of sound effects to portray its creepy aliens.

But the show was never going to rise or fall on the strength of the vfx. It clicks because of the emotional drama of the characters’ struggles, as brought to life by Wyle and a strong supporting cast. That kind of heart was the key ingredient that was lacking in “Terra Nova,” which went one season and out.

Still, a sci-fi venture was initially a risky proposition for TNT, which was known for meat-and-potatoes procedural fare like “The Closer” and “Rizzoli & Isles.” But it was a bet TNT programming chief Michael Wright was ready to take, thanks to the strength of the network’s relationship with Spielberg, which dates back to the sweeping 2005 Western miniseries “Into the West.” Amblin has a handful of new projects percolating at TNT, including a fresh take on the vintage detective drama “Peter Gunn.”

“Steven and his team are the most creative, most responsible partners we’ve ever had. They really care about what they’re doing,” Wright says. “We always want our shows to be commercially accessible without sacrificing intelligent storytelling. With ‘Falling Skies,’ they hit it dead center.”