BOSTON -- They were hoping for a peaceful race, and they got one.

Under sunny skies, spectators packed the course for Monday's Boston Marathon, which went off without a hitch in a city still in recovery mode after last year's deadly bombings.

Less visible was a new multipronged security apparatus involving federal, state and local law enforcement that kept spectators and competitors safe and will likely serve as a model for other "soft footprint" security operations at large-scale gatherings in New York and nationwide, officials said.

"We . . . don't want to have it, you know, kind of a race through a militarized zone," said Massachusetts Gov. Deval Patrick during a discussion before the race about enhanced security measures after last year's bombings. "So it's about striking a balance, and I think we have struck that balance."

Monday's anti-terrorism operation was drafted in the days and months following the twin bombings near the finish line that killed Martin Richard, 8, Krystle Campbell, 29, and Lingzi Lu, 23 and injured 264. MIT police officer Sean Collier, 27, died several days later during the manhunt for the Tamerlan and Dzhokhar Tsarnaev, the Boston-area brothers suspected of the bombings and Collier's killing. Tamerlan Tsarnaev was killed in a shootout with police. Dzhokhar Tsarnaev is awaiting trial on multiple charges.

The security plan opted for a strategy where some security assets wouldn't be apparent -- but would still thwart anyone intent on doing harm.

The FBI, Boston and state police, along with other law enforcement agencies, dispatched hundreds of plain clothes cops and agents to walk the marathon route; mounted dozens of security cameras; used radiation wands and detectors; put snipers on standby; and meticulously checked bags and backpacks like the ones used to conceal the pressure cooker bombs that detonated at last year's race.

Other new security measures included increased aerial surveillance, explosive-proof trash cans, and additional bomb-sniffing dogs, authorities said.

About 3,500 law enforcement officers were assigned to the race. At 6 a.m. more than 100 National Guard soldiers walked the race route in a show of force aimed at deterring potential attacks.

Officials said local and federal authorities spent months preparing the unprecedented security operation, drawing on lessons from other large events including last year's New York City Marathon and Macy's Thanksgiving Day Parade.

After coming under scrutiny for not passing along intelligence about the Tsarnaev brothers, the FBI worked closely with Boston police, sharing all relevant chatter and leads concerning possible security concerns, officials said.

"There was unprecedented cooperation this year," said a federal law enforcement official. "Everything we knew" local law enforcement knew . . . "The national security leadership is very happy with the way today's race turned out. For the marathon to go off without incident is a validation of our plans."

"Soft footprint," which refers to the relatively low-key but still all-encompassing security measures used Monday, will likely serve as a template for events across the country, the law enforcement official said.

Runners and race spectators said they were pleased with marathon security because there was a feeling of safety but not intrusion.

"I felt totally at ease, because it was secure without being a police state," said Marge Culver, 46, of Boston, as she cheered on several relatives running the marathon. "They could have overwhelmed us with uniforms, but they didn't and still kept us safe."

Marathoner Jackie Bates, a Manhattan resident who works in Garden City, said "by taking back the finish line this year, we beat those who wish us harm. This year's not about hate, only love."