The people of China are used to armies on the march. Military movements of one kind or another have, after all, played a central role in Chinese history, from the terracotta soldiers which once escorted Chinese emperors to the afterlife to the 6,000-mile march which, in 1936, gave Mao Zedong's forces victory over the Kuomintang.
But as more than 50,000 athletes, volunteers and event officials from all over the world assemble in Shanghai for the 2007 Special Olympics World Summer Games, it's clear that this is another kind of invasion altogether. This is the goodwill army, and its weapon of choice is the smile.
At Pudong International Airport, a sea of green T-shirts flowing down the immaculate escalators announced the arrival of the 200-strong brigade of Irish volunteers who have come to join the 143 athletes of Team Ireland and their families. One visiting Irishman solemnly doffed his green cowboy hat to a young Chinese official, who blushed and giggled as she hurried about her business.
Meanwhile, another Irishman caused a mini-riot when he turned up unannounced yesterday evening in the hotel where the volunteers are based. The actor Colin Farrell's role as master of ceremonies for this afternoon's opening ceremony at the 80,000-seater Shanghai Stadium was supposed to be a closely-guarded secret - but the Irish bush telegraph is, obviously, working at full tilt in Shanghai.
The Special Olympics was set up as a day camp in the 1960s by Eunice Kennedy Shriver, sister of John F Kennedy. It now provides year-round sports training and athletic competition to more than two million children and adults with learning disabilities in 160 countries.
And as anyone who has even the most fleeting acquaintance with this astonishing worldwide endeavour will tell you, winning isn't necessarily about coming first. "Let me win," the Special Olympic athlete's oath famously states. "But if I cannot win, let me be brave in the attempt."
Over the next 10 days Irish athletes of various ability levels will compete in aquatics, athletics, badminton, basketball, bowling and bocce (a specialised kind of bowling), equestrian sports, football, golf, gymnastics and table tennis.
The sporting menu in Shanghai will also offer many colourful activities with a local flavour, including kayaking, judo and dragon boat racing.
There are, many who wonder whether holding the games here is an exercise in global cynicism. The 2007 Special Olympics World Summer Games is the first of three huge, high-profile events which are being staged in China for the first time.
It will be followed by the Olympics in Beijing next year; and in 2010, Shanghai will be back in the spotlight when the city hosts the World Expo. Political considerations play a major role in this - as do commercial ones.
The Irish volunteers spent their first evening at a reception hosted by Enterprise Ireland, where they learned that Irish exports to China € reached 1.4 billion last year.
In 1999 there were just five Irish companies operating in China: there are now 55, most of which specialise in electronics and information technology.
According to the Asia director of Enterprise Ireland, Michael Garvey, that trend is likely to continue - although Irish companies face stiff competition in the scramble to capitalise on the vast potential market.
For the duration of the Special Olympics, it will be interesting to see what effect this benign temporary invasion will have on China's carefully-controlled culture . The authorities in Shanghai, a city of 19 million, have given the games top billing. Many buildings boast enormous banners with pictures of smiling Chinese athletes and, inevitably, slogans. One of these reads: "Get Every One To Care People Suffering from ID [ Intellectual Disability], and support the Endeavour to Promote Special Olympics". Which might not be particularly catchy but, according to the chief executive of Special Olympics Ireland, Mary Davis, gets to the heart of matters. "I think what these games can bring to China is huge awareness in the whole area of disability," she says.
What are her hopes for Team Ireland in this competition?
"I would love to see them do their very, very best. And if they can exceed their best in any way, that's fantastic."