Largest police detail ever at Macy's Thanksgiving Day Parade

NEW YORK CITY --President Obama assured the nation Wednesday that law enforcement was on the case in the wake of the Paris attacks.

And there were plenty of cops at the premiere Thanksgiving Day event Thursday: the Macy's Thanksgiving Day Parade.

The largest contingent of heavily-armed police officers in New York City's history stood along the parade's two and a half mile long route.

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NYPD Officers at the Macy's Thanksgiving Day Parade CBS News

They were protecting the 3.5 million onlookers who crowded streets, twenty deep in some places. Some were concerned about terrorism -- some, not.

Undercover cops moved among them and sniper teams scanned from rooftops.

In downtown Manhattan, dozens of officers also kept an eye on things in a massive room named the joint operations center. Chief James O'Neill gave CBS News a tour, including the gigantic screens that line the room.

"We have access to so many cameras throughout the city that we can choose. If there's an event somewhere in the city, we can go right to that neighborhood," said O'Neill.

During major events like parades, the operations center is also staffed with representatives of various state and federal agencies.

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NYPD Joint Operations Center CBS News

"I spend most of my time planning to make sure that in the event that something does happen, we respond quickly and effectively," O'Neill said. "We stood up two new units -- the critical response command and the strategic response group -- so we have anywhere up to 800 people available to respond to any incident."

Security ramped up for holiday weekend

The nature of terror attacks has shifted to the use of automatic weapons and suicide vests. The NYPD has adopted new rules of engagement, meaning officers will respond more quickly with deadly force.

"We've responded by retraining our personnel and are in the process of my 35,000 [officers], to get in and neutralize the threat as fast as possible," said NYPD Commissioner Bill Bratton.

Security has also been stepped up in airports across the nation. Over two million passengers will travel through Los Angeles International Airport this weekend.

Officials insist there are no specific, credible threats in this country, but a recent poll shows most Americans consider the risk of terrorism the most important problem facing the nation.