China’s splendid display of troops and weapons at its 70th anniversary celebration on Tuesday was “a military show of strength” amid economic challenges, one professor told CNBC.”(China has) got a lot of problems, but today is the day that they want to show an image of great confidence, pride, and strength,” professor at University of California San Diego, Susan Shirk, said Tuesday.The celebrations, which boasted one of Beijing’s largest military parades, took place as China faces economic and political challenges. Even as tens of thousands were celebrating National Day in China, demonstrators in the territory of Hong Kong marched through the streets in its 17th week of protests.In Beijing, Chinese President Xi Jinping, addressed the nation and pledged that “No force can stop the Chinese people and the Chinese nation forging ahead.”The military parade, with all its pomp and pageantry, involved more than 15,000 military personnel who took part in celebrations commemorating the Chinese Communist Party’s 70 years of rule. On display were 160 aircraft and 580 pieces of military equipment, including drones and missiles. The Dongfeng 41, a nuclear-capable missile, was also unveiled during the military parade. The Associated Press quoted analysts as saying the weapon could reach the U.S. in 30 minutes.”It looks like this is almost entirely, if not entirely, a military show of strength,” Shirk told CNBC’s Street Signs.Military vehicles drive in a military parade at Tiananmen Square in Beijing on October 1, 2019, to mark the 70th anniversary of the founding of the Peoples Republic of China.Greg Baker | AFP | Getty ImagesThis was a stark difference from China’s 35th anniversary parade, Shirk said. While this year’s parade focused on national security, the edition some three decades ago showcased China’s prosperity, she added.Referring to the 2019 parade, Shirk said that “the image that Xi Jinping wants to show to his people and to the world is one of a strong country … where the focus is much more on national security.”In comparison, the 35th anniversary parade was about the “prosperity that market reforms were bringing to China,” she said. At that time, “the floats were things like a big refrigerator filled with mostly beer,” she said, adding that Beijing wanted to showcase Chinese consumption and how people’s lives had improved then.But the world’s second-largest economy has been under increasing economic pressure recently. The country is facing slowing domestic growth amid a protracted trade war with the U.S. and a global slowdown.An outbreak of African swine flu has also pushed up food prices, adding to further pressure on the economy, said Shirk.According to the UN’s Food and Agriculture Organization, the highly contagious and fatal viral infection has led to the culling of some 1.17 million hogs in China. The country is a major producer and consumer of pork.In August, food prices were up by 10% year-on-year, according to data from China’s National Bureau of Statistics. July’s food price inflation, meanwhile, jumped 9.1% compared to a year ago.— CNBC’s Evelyn Cheng contributed to this report.