Shortly after the occupying Nazi army goose-stepped into Greece in the spring of 1941, officers of the Wehrmacht entered Athens’ neoclassical National Archaeological Museum. Their goal: To take possession of a treasure of antiquities — a statue of Zeus, the Mask of Agamemnon and thousands of other pieces — and return all to the fatherland as their leader had ordered.

Along with his “Final Solution” for the Jews — some 70,000 would be exterminated in Greece alone — and his desire to eventually rule the world, Adolph Hitler bizarrely believed that ancient Greece was founded by Aryans. Thus he had instructed his Nazi classicists to pull from the earth what he thought would be Germanic finds, finally proving the connection with ancient Greece.

But they had no success, because there were no such finds. They came away empty-handed, as  did the shocked Nazi officers who had entered the museum in Athens with high expectations Instead, all of the treasures were gone — many buried underground as insurance against the Nazi occupation.

As author Stephan Talty writes in his new book, “The American School of Spies: The Archaeologists Who Fought the Nazis and Saved the Treasures of Ancient Greece” (Dutton), “The relics were all saved.”

Talty’s in-depth account reads like a real-life Indiana Jones story, focusing on the efforts of classicists and archaeologists to save the ancient Greek artifacts from Hitler.

For years, the Nazis claimed “Aryans were the creators of the world’s first great civilization…Hitler and his lieutenants were fixated, in varying degrees, on ancient Greece and its artifacts,” according to the author.

Hitler was especially “besotted” by a “crouched, naked male athlete [known as] the Discobolus,” or discus thrower, Talty writes. The statue was celebrated in “Olympia,” filmmaker Leni Riefenstahl’s propagandist documentary about the 1936 Olympics.

To do battle against the Nazi occupation of Greece, as well as Hitler’s agenda to capture the antiquities, President Franklin Delano Roosevelt assigned Army General William “Wild Bill” Donovan, head of America’s Office of Strategic Services (OSS) — the precursor to the CIA — to create a clandestine intelligence team.

Donovan made his way to Greece and was “impressed” by the citizens’ “high morale,” writes the author. On the general’s return home, he decided that a “classic spy network” be formed because, controversially, he believed that the “Allies couldn’t rely on conventional forces alone to defeat the Germans.”

The plan was to establish small guerrilla units, with manpower coming from Greek immigrant communities in the US, of “spies and the commandos” to stop the Nazis. Donovan hit up Harvard and Yale grads in his recruitment for “secret agents.” He also needed someone very tuned-in and risk-taking to run the clandestine operation — essentially, a “spymaster,” reveals Talty.

Donovan chose Rodney Young, a handsome 33-year-old American archeologist with no military experience, but who had worked on digs in Greece, to pull the team together and form what became known in Washington as the “Greek Desk.”

Young’s real job: to turn the epigraphers, scholars, classicists and archaeologists into spies.

A rich kid with impressive credentials, Young is described by Talty as “an East Coast blue blood.” His mother was a member of the Ballantine family, Scottish rivals to American beer dynasties like Pabst. The future spymaster had grown up in a Greek Revival mansion in Newark, NJ, and a country home in Bernardsville. He learned Greek at the exclusive St. Paul’s School in New Hampshire and studied at Princeton like his forebears.

He was also known as a party guy, and once described as the “Cary Grant-ish darling of New York debutante balls,” writes Talty.

Young eventually settled in Athens at the famed American School of Classical Studies, which became his home base. But not long after the Nazi occupation, he was struck by shrapnel from an explosion, and his intestines and stomach wall were penetrated. According to the author, an Athens newspaper reported that “new American blood is now added to that shed in 1821 for Greek independence.”

Recovering from his injuries, Young continued running the Greek Desk and training his operatives — including Dorothy Hannah Cox, a 50-year-old “spirited, tough” excavation architect and expert in ancient coins. The OSS offered her a role as a secret agent, with the idea that she would use her job working for Greek War Relief as a cover.

As Talty writes, “Using archaeology as a cover for espionage was controversial.” Scholar-secret agents like Cox and Young were once accused of “prostituting science,” as one of their peers put it.

In July 1942, the recruits, mostly Greek-Americans, began four weeks of basic training in spy craft: from how to create a cover identity to how to fatally knife a Nazi sentry, along with learning codes and cryptography.

As the author observes, “America had little experience in foreign espionage, and General Donovan and his lieutenants in many ways were making it up as they went along.”

Young was given the code name Pigeon; Dorothy Cox was Thrush. Their secret training camp, a site known as the “Farm” was a former horse estate in Virginia, 20 miles outside of Washington.

The two agents had grown up in comfortable homes. Now they were told by their OSS superior to forget all that and “wage war in the old, savage way,” writes Talty.

Along with spy school, Donovan established a commando unit made up of the American-born sons of immigrants who, as the author notes, were “presumably ready and willing to kill the occupiers of their ancestral homelands.”

In January 1943, FDR signed an executive order creating an infantry battalion made up of second-generation young American men “who would fight in the places their parents had left,” writes Talty. While 1,200 “cocky and wild” recruits were shipped to Camp Carson in Colorado to be trained, that number was reduced to 212 who headed to Greece to fight the good fight.

“They were returning to liberate their parents’ homeland,” the author writes.

Fast forward to June 4, 1946 and a ceremony in one of the grand halls of the National Archaeological Museum in Athens. With a gathering of curators and Athenians present, workers dug up buried antiquities kept hidden from the Nazis throughout the war.

“It would take another two years for the museum to be ready for opening. And in 2013, writes Talty, “the Greek Ministry of Culture announced the return of more than 10,000 relics, all taken by the Nazis.”

Young had escaped death by Nazi marauders but, in 1974, was killed in an auto accident.

 “For years afterward,” writes Talty, “visitors to the [University of Pennsylvania’s] archaeology department would find his office ‘sealed like a shrine.’ He was the last of a particular breed.”