The buses leave Saturday before sunrise, carrying dozens of Philadelphia police officers to New York City.
Active officers, making the trip on a day off to pay final respects to a fallen brother.
Retired officers, wanting to show support.
And a class of police cadets, who will see firsthand, for perhaps the first time, the degree of sacrifice demanded of them.
They go even as their own department has received threats against officers in recent days.
The Philadelphia police will join a contingent of officers from departments large and small from around the region and country, all bound for the funeral of Officer Rafael Ramos, 40, who along with his partner was shot and killed a week ago in a patrol car in Brooklyn by a gunman targeting police.
"It's a brotherhood," said Fraternal Order of Police Lodge 5 president John McNesby. "And it's a fragile time."
The thousands of officers who will stand at attention outside Christ Tabernacle Church in Queens to pay respect to Ramos - and to show support to his widow and two sons - will do so amid continuing protests against police across the country. The demonstrations erupted in the aftermath of the deaths of Michael Brown, an unarmed teen shot and killed by a police officer in Ferguson, Mo., and Eric Garner of Staten Island, also unarmed, who died after he was placed in a police choke hold.
New York police union officials say their officers have been betrayed by politicians who have fostered protest, fueling a poisonous environment between police and citizens - an environment that led to the deaths of Ramos and his partner, Officer Wenjian Liu, 32, outside a Brooklyn housing project.
"With all the second-guessing and professional protesting of officers going on, we thought we better show a large contingent of unity," he said.
Philadelphia Police Commissioner Charles H. Ramsey said Friday that he had spoken with New York Commissioner William Bratton multiple times since the killings, offering his support and assistance. The NYPD is always there for the Philadelphia department in times of tragedy, he said.
Like New York, Ramsey said, the Philadelphia department has received threats of violence against officers in recent days.
Officers have been warned to be more vigilant, he said. No arrests have been made.
Ramsey would not discuss the threats in detail, saying he didn't want to draw attention that would "attract more nuts."
Instead, he lauded the two busloads of Philadelphia police heading to New York.
"It is important that we show support for one another," he said.
It was a sentiment shared by law enforcement officials across the region.
Bensalem Public Safety Director Fred Harran, a Brooklyn native, said he and seven officers would go to New York for the funerals.
"This is our way of showing our feelings," Harran said. "Police don't go out and burn down a Nike store or loot a liquor store. This is our way of showing solidarity. And then we'll be back to work, treating everyone fairly. And I mean everybody, even the criminals.
"In light of the climate of the nation, we have to show our solidarity, and we have to support one another," Harran said.
"We have incredible support in Bucks County. But leaders nationally and New York City's mayor don't support local law enforcement."
The region's contingent of police at the funeral will include more than 20 officers from the Camden County Police.
They will be "standing in solidarity with the hundreds of thousands of police officers throughout the nation to show support for a colleague killed in the line of duty," county spokesman Dan Keashen said.
Eight officers from the Upper Darby department are taking police cruisers, traveling on their own time, Police Superintendent Mike Chitwood said.
Plymouth Township Police Chief Joseph F. Lawrence and three to five officers will go from that department.
"It really is as simple as, we want to pay our respects," said Lt. Jeff O'Brien, who also will attend. "Especially in light of, in the not-too-distant past, losing an officer of our own."
In 2012, Plymouth Officer Bradley Fox was fatally shot while pursuing a hit-and-run suspect on foot. Mourners at his funeral came from a wide area, including Chicago and Canada.
Chief Thomas Nestel III, commander of the SEPTA police, said his department was sending a 15-person contingent.
He said that he received an "overwhelming" response from his officers when he asked for volunteers.
"The assassinations have hit every police officer in this country really hard," he said.
The Ramos funeral, he said, is a step toward healing.
"Everyone wants to show the NYPD that we're together on this and the police are strong," he said.
He said so many of his officers had offered to go to the funeral that he had to turn some down.
"I actually had to limit the number of people I was sending," Nestel said. "So many volunteered that I'd have nobody working the streets."
Contributing to this article were Inquirer staff writers Ben Finley, Michaelle Bond, Laura McCrystal, and Melanie Burney.