On a brisk Sunday in Depression-era Philadelphia, two bombs — one real, the other metaphorical – were ignited in Philadelphia.

At 3:30 a.m. that Feb. 20, 1938, a device packed with metal scraps detonated on the N. 4th Street doorstep of a German-American meeting hall that had hosted rallies for Nazi sympathizers. Surrounding buildings were damaged but, except for a couple knocked out of bed, no one was hurt.

A few hours later and five miles away, in a lofty suite at Center City's Ritz-Carlton hotel, National Football League owners unintentionally touched off another explosion, though the  after-shocks from this one would not be felt for another 80 years.

That afternoon, the second and last day of its annual meetings, the young league's leaders expanded rosters to 30, tinkered with the kickoff rules and, just two weeks after a brawl-filled Bears-Redskins exhibition in Miami, outlawed most postseason games.

And then, at a session of the five-man Rules Committee chaired by Bears owner George Halas and including Eagles boss Bert Bell, Redskins owner George Preston Marshall proposed that a 15-yard unsportsmanlike-conduct penalty be assessed any time a defender physically maltreated a passer.

In the midst of an NFL season when roughing penalties on players like the Eagles' Michael Bennett and Green Bay's Clay Matthews Jr. have brought it into the national spotlight, the roughing-the-passer penalty has never been more controversial.

In some ways, not much has changed in a league where the bottom line has always been a top concern. Then as now, the rule's intent was to protect not just the passer but the owners' significant investment.

Not long before seeing the new rule, Marshall had signed his young passing star, Slingin' Sammy Baugh, to an unprecedented, three-year, $25,000 contract.

Since passing anywhere behind the line had become legal in 1933, the popularity of football's aerial game – both as a tactic and an attraction – had increased in a sport long dominated by the run.

In that 1937 season, Baugh, though still technically a single-wing tailback, had helped revolutionize football.

Utilizing the pass more effectively than anyone ever had, Baugh led his Redskins to a championship. In that title victory over Chicago, he'd passed for an astounding 335 yards, a championship-game total no rookie QB would surpass for 75 years.

In 1936, NFL teams had averaged fewer than 12 points and six completions a game. Baugh set a completion record (81) in '37 and threw for 1,127 yards. A decade later, he'd amass nearly 3,000 yards (2,938). So versatile was the tall Texan that in 1943 he led the league in passing, interceptions and punting.

"What Babe Ruth's home runs did for baseball in the early 1920s, Baugh's bombs did for the NFL in the late '30s," Washington Post columnist Thomas Bosewll would write.

But that instant success immediately made Baugh and his imitators a target in the black-and-blue world of pro football.

"The rules didn't give any protection to the passers," Baugh recalled decades later. "Those linemen could hit the passer until the whistle blew. … The ball could be 50 yards down the field and the bunch could still hit you.

"A passer had to learn to throw and move. You never saw him just stand there, watching. You had to protect yourself because [they] were going to flatten you every time. If you were a good ballplayer, they tried to get you out of there."

So the penurious Marshall determined to protect that investment. A few weeks before coming to Philadelphia, he'd summoned Baugh to his office.

"`What if we could get a rule put in that after a passer threw the ball, they couldn't run him down and knock him around?" Baugh, who died at age 94 in 2008, recalled him asking. "I said, 'Do that and the passer will play about 10 years longer.' And he picked up the phone and called George Halas."

At the Ritz-Carlton, owned by Bell's family, Marshall reiterated his concerns to Halas and the committee.

"If we don't put in some kind of a rule, all the passers are going to get killed," said Marshall, likely concerned only about his own.

Such a rule had existed in college football since 1914, part of the sweeping reforms that followed a spate of player deaths and subsequent calls to outlaw the violent game.

Convinced, the owners approved Marshall's roughing-the-passer proposal. In Baugh's case, at least, it worked. The only serious injury he sustained in those years, he said, happened at his Texas ranch where a kicking calf broke his ribs.

By 1940, the Redskins had transitioned to the T formation to take advantage of Baugh's talents. That year they again faced the Bears in the NFL title game. This time Chicago triumphed, 73-0, still the most lopsided score in championship history.

Asked afterward if the outcome might have been different had his Redskins scored on their opening drive, Baugh didn't hesitate.

"Yeah, it would have been 73-7."