But several of the men said they were ready to kill and die "in the name of Allah", court records said.
Their goal was "to kill as many soldiers as possible" in attacks with mortars, rocket-propelled grenades and guns, prosecutors said.
They also allegedly spoke of attacking a UN navy base in Philadelphia during the annual Army-Navy football game, when the place would be full of sailors, and conducted surveillance at other military installations in the region.
Christopher Christie, a US attorney, said: "This was a serious plot put together by people who were intent on harming Americans.
"We're very gratified federal law enforcement was able to catch these people before they acted and took innocent life."
Investigators said they infiltrated the group with an informant well over a year ago and bided their time while they secretly recorded the defendants, five of whom lived in Cherry Hill, a Philadelphia suburb about 32km from Fort Dix.
The six were arrested on Monday night trying to buy AK-47s, M-16s and other weapons from an FBI informant, the authorities said.
They were scheduled to appear before a federal judge in Camden on Tuesday afternoon to face charges of conspiracy to kill US servicemen.
Four of the men were born in the former Yugoslavia, one was born in Jordan and one came from Turkey, authorities said.
All had lived in the United States for years. Three were in the United States illegally; two had green cards allowing them to stay in this country permanently; and the sixth is a US citizen.
Asked if those arrested had any links to al-Qaeda, Tony Snow, the White House spokesman, said it appeared "there is no direct evidence of a foreign terrorist tie".
In court documents, prosecutors said the suspects came to the attention of authorities in January 2006 when a shopkeeper alerted the FBI about a "disturbing" video he had been asked to copy onto a DVD.
The video showed 10 young men in their early 20s "shooting assault weapons at a firing range ... while calling for jihad and shouting in Arabic 'Allahu Akbar' [God is great]", the complaint said. The 10 included six of those arrested, authorities said.
By March 2006, the group had been infiltrated by an informant who developed a relationship with Shnewer, and the informant secretly recorded meetings last August, according to court documents.
Christie said one of the suspects worked at Super Mario's Pizza in nearby Cookstown and delivered pizzas to the base, using that opportunity to scout out Fort Dix for an attack.
"Clearly, one of the guys had an intimate knowledge of the base from having been there delivering pizzas," Christie said.
The men also allegedly conducted surveillance at other area military installations, including Fort Monmouth in New Jersey, Dover Air Force Base in Delaware, and a Philadelphia Coast Guard station.
Besides Shnewer, Tatar and Duka, the other three men were identified in court papers as Dritan Duka, Shain Duka and Agron Abdullahu.
Fort Dix is used to train soldiers, particularly reservists. It also housed refugees from Kosovo in 1999.