It would take more than a month for the US to give Beijing a full explanation: that a series of basic errors had led to five GPS-guided bombs striking China's embassy - including one that hurtled through the roof of the ambassador's residence next to the main building but didn't explode, likely sparing his life.
The real target, officials said, was the headquarters of the Yugoslav Federal Directorate for Supply and Procurement (FDSP) - a state agency that imported and exported defence equipment. The grey office building is still there today - hundreds of metres down the road from the embassy site.
Nato had initially hoped the bombing campaign would only last a few days until Milosevic gave up, pulled his forces out of Kosovo and allowed peacekeepers in. But by the time the embassy was hit it had stretched to more than six weeks. In the rush to find hundreds of new targets to sustain the aerial assault, the CIA, which was not normally involved in target-picking, had decided the FDSP should be struck.
But America's premier intelligence agency said it had used a bad map.
"In simple terms, one of our planes attacked the wrong target because the bombing instructions were based on an outdated map," US defence secretary William Cohen said two days after the bombing. He was referring to a US government map that apparently did not show the correct location of the Chinese embassy nor the FDSP.
All US intelligence officers had was an address for the FDSP - 2 Bulevar Umetnosti - and a basic military navigation technique was used to approximate its co-ordinates. The technique used was so imprecise, CIA chief George Tenet later said, that it should never have been used to pick out a target for aerial bombing.
To compound the initial error, Tenet said, intelligence and military databases used to cross-check targets did not have the embassy's new location listed, despite the fact that many US diplomats had actually been inside the building.
Had anyone on the ground visited the site to be bombed they would have found a gated compound, a five-storey building with a green-tiled oriental sloped roof, a bronze plaque announcing the embassy's presence and a large, bright red Chinese flag fluttering more than 10 metres in the air.
IMAGE SOURCE,SASA STANKOVIC/EPA/REX/SHUTTERSTOCK
Image caption,
The front of the embassy was largely undamaged
The crux of the CIA's explanation was hard for many to believe: the world's most advanced military had bombed a fellow UN Security Council member and one of the most vocal opponents of the Nato air campaign because of a mapping error. China was having none of it. The story, it said, was "not convincing".
"The Chinese government and people cannot accept the conclusion that the bombing was a mistake," the foreign minister told a US envoy sent to Beijing in June 1999 to explain what had happened.
But why would the US intentionally attack China?
It wasn't long after the Sun rose on the morning of Saturday, 8 May 1999, that David Rank, a US diplomat, got out of bed in Beijing.
He turned on the television and switched to CNN. The American news network was carrying live pictures of the smouldering Chinese embassy in pitch-dark Belgrade.
By that afternoon, thousands of irate Chinese protesters would be gathered outside. But Rank, at that stage, was fairly calm. He rang his boss, the head of the political section: "I said, you know, Jim, this is the damndest thing."
The diplomat rushed from his residence to the embassy down the road, where US officials were trying to figure out what had happened. Something had clearly gone wrong but this must have been,
had to have been, a tragic mistake.
"It was so patently obvious that it was a sort of fog of war accident… At that point I didn't think that down the road this was going to be a major problem. Obviously, it was a major problem, but not the sort of convulsive incident that it turned out to be," said Rank.
But in the next hours, the shape of how the Chinese government and people would respond started to become clear.
IMAGE SOURCE,PETER ROGERS/GETTY IMAGES
Rank began receiving calls from liberal Chinese friends who were outraged at the bombing. American journalists got similar calls from Chinese contacts with pro-US views, expressing shock and a sense of betrayal.
Chinese state media was already laying out a clear narrative - the US had breached international law by bombing a Chinese diplomatic outpost. "The language that I heard from lots and lots of Chinese, it was identical. It was the same almost word-for-word lines of real anger," said Rank.
By that afternoon thousands of students were streaming onto the streets of Beijing. They gathered outside the embassy and things quickly turned violent.
"They were pulling up the paving stones. Beijing sidewalks aren't paved, they have big tiles and they were pulling those up and smashing them and throwing them over the walls."
IMAGE SOURCE,PETER ROGERS/GETTY IMAGES
Many of those bits of concrete were crashing through the windows of a building where more than a dozen embassy staff, including US Ambassador James Sasser, had hunkered down. Embassy cars were being defaced and attacked.
The message was clear: the bombing was intentional and, as one slogan went, "the blood of Chinese must be repaid". The protests would continue the next day, with even more people - some reports said 100,000 - storming the diplomatic district, and pelting stones, paint, eggs and concrete at the British and American embassies.
"We feel like we're hostages," Bill Palmer, an embassy spokesman trapped in one of the buildings, said at the time.
Demonstrations of this scale had not been seen in tightly-controlled China in the decade since students led a pro-democracy uprising in Beijing's Tiananmen Square in 1989. This time the anger was directed away from the Communist Party but, with the 10th anniversary of the crackdown on students in Tiananmen approaching, the government had to strike a balance between giving vent to public anger and remaining in control.
In a rare TV address Vice-President Hu Jintao endorsed the protests but also warned they had to remain "in accordance with the law".
IMAGE SOURCE,REUTERS
Image caption,
US Ambassador James Sasser was trapped in the embassy for four days as protests raged
The uproar was not isolated to Beijing. Crowds also took to the streets of Shanghai and other cities that weekend. In central Chengdu, the US consul's residence was set alight.
Weiping Qin, a then 19-year-old student leader at the maritime college in southern Guangzhou city, said demonstrators were not informed that Nato had already apologised for what it said was an accident. "The government was hiding this important message. They didn't tell us - so young people, everybody, felt angry. We just wanted to go in the streets and protest against the United States."
He said that initially students at his college were told they had to stay in their dormitories. But 24 hours after the bombing, the university leadership told him that they needed 30,000 students in the streets around the US consulate - 500 of whom would come from the maritime college.
The fired-up students drew lots to choose who could attend. They were loaded onto buses and given statements to read that echoed the stilted official language being broadcast by state media. "They gave us long sentences. But in the street, to speak out in long sentences is very hard." He decided to yell slogans about the evils of Nato and the US instead.
IMAGE SOURCE,WEIPING QIN
Image caption,
Weiping Qin (right) was a student leader at Guangzhou Maritime College in 1999
The night the US bombed a Chinese embassy