In bunkers now held by ISIS militants, and sometimes in streets emptied by bomb threats, scores of American service members secretly helped find and dispose of Saddam Hussein's aging chemical weapons. Now stateside, many troops are sick with mystery ailments the military has at times tried to conceal.

Those are the broad strokes of an exhaustive 8,500-word New York Times multimedia package tonight by conflict reporter C.J. Chivers and videographer Mac William Bishop. It reveals the existence of far more chemical munitions in pre-invasion Iraq than anyone had previously acknowledged, but details the disheartening aftermath for U.S. service members who secured those munitions, often finding them in IEDs planted by insurgents after American troops flooded into the country in 2003:

From 2004 to 2011, American and American-trained Iraqi troops repeatedly encountered, and on at least six occasions were wounded by, chemical weapons remaining from years earlier in Saddam Hussein's rule.

In all, American troops secretly reported finding roughly 5,000 chemical warheads, shells or aviation bombs, according to interviews with dozens of participants, Iraqi and American officials, and heavily redacted intelligence documents obtained under the Freedom of Information Act.

The story is likely to be bandied about as a political football, particularly by conservatives who might think it vindicates the Bush administration's pretext for invading Iraq. (The smarm started on Twitter even before the full story was published.) But Chivers clearly points out, in print and in video narration, that the rocket and artillery rounds, filled with mustard gas or sarin nerve agent, were not what the White House promised: pre-1991 vintage, in such serious disrepair that they couldn't be used as intended, and hardly a secret—their existence had been confirmed by the DOD and UN in 2006, albeit in far smaller numbers than the Times report found.

There's one other issue, according to the Times: "The publicly released information also skirted the fact that most of the chemical artillery shells were traceable to the West, some tied to the United States."

In fact, part of the reason much of the evidence for these weapons was concealed, Chivers writes, was because they contradicted the Iraq war hawks' rationale:

Participants in the chemical weapons discoveries said the United States suppressed knowledge of finds for multiple reasons, including that the government bristled at further acknowledgment it had been wrong. "They needed something to say that after Sept. 11 Saddam used chemical rounds," Mr. Lampier said. "And all of this was from the pre-1991 era."

Rather, the story is about the uniformed personnel who have essentially gotten shafted by the bureaucracy they served:

The New York Times found 17 American service members and seven Iraqi police officers who were exposed to nerve or mustard agents after 2003. American officials said that the actual tally of exposed troops was slightly higher, but that the government's official count was classified.

The secrecy fit a pattern. Since the outset of the war, the scale of the United States' encounters with chemical weapons in Iraq was neither publicly shared nor widely circulated within the military. These encounters carry worrisome implications now that the Islamic State, a Qaeda splinter group, controls much of the territory where the weapons were found.

The American government withheld word about its discoveries even from troops it sent into harm's way and from military doctors. The government's secrecy, victims and participants said, prevented troops in some of the war's most dangerous jobs from receiving proper medical care and official recognition of their wounds.

The story goes on at length to detail, for example, precisely how the Iraqi chemical-weapons stockpiles came to be, and how U.S. and other Western companies helped in the process. But mainly it focuses on the servicemembers, explosive ordnance disposal experts, who experienced mustard burns, got "bit" by sarin gas, and who often couldn't obtain adequate care because the cause of their maladies wasn't believed by many doctors to exist.

Two soldiers helped recover a shell from a roadside bomb in 2004 off Route Irish—the deadly road from Baghdad's airport to the Green Zone—that ended up oozing sarin nerve gas and debilitating them. They received primary treatment but returned back to the field soon after:

In June the two soldiers, still suffering symptoms, including intense headaches and difficulties with balance, asked to return to duty. Soon they were ordered to a site hit by 60-millimeter mortar fire.

Two shells had been duds. They were stuck, fins up, in the sand. Sergeant Burns freed them with rope and then set off carrying them to a disposal pit.

"I was walking with one in each hand, and I just fell," he said. "I remember falling and trying to keep the fuses from hitting the ground."

He wondered why the Army had not sent the two of them home. "We really should not have been operating out there," he said.

As the insurgency gained steam and the U.S. mission transitioned from toppling Saddam to slowing civil war, the WMD-recovery mission became a lower priority, Chivers writes—and for the soldiers and sailors and Marines who did find chemical munitions, critical safety and recordkeeping procedures were often skipped.

Mustard, sarin, or blister agent: The cases often sounded similar. Soldiers would report a not-quite-right feeling, a rotten smell perhaps, and a sensation of hair on the back of their necks standing up. Soon they were blistered, or wheezing, or dizzy and lightheaded. Often they were sworn to secrecy and treated as if they were on drugs, they said. Many were not only denied the correct ongoing medical tests and care but military decorations, such as Purple Hearts, to which they believe they're entitled.

Spurred on by the Times' prodding, military representatives have said they now want to locate all the affected service members and make sure they receive their due, medically and professionally.

But the long story ends on an ominous note, reporting that the largest source of the chemical arms, a single base complex, was supposed to be entombed in solid concrete by Iraq's new government: "The compound, never entombed, is now controlled by the Islamic State."

[Video screenshot courtesy of the New York Times]