For 21 years, the bombardment was fairly constant - the People's Liberation Army would fire artillery at the Taiwanese-controlled island of Quemoy, just 10km off the Fujian coast, and Taiwan would occasionally lob shells back at the mainland coast. People in the firing line built bomb shelters and made up songs about the attacks. The shelling began in 1958 with a 44-day, 480,000-shell barrage that almost exhausted the PLA's munitions supplies. Then, the liberation army was at the forefront of the mainland's efforts to reclaim the island - but that stopped on New Year's Day 1979, when then defence minister Xu Xiangqian announced an end to the campaign. The ceasefire did not mean an end to Beijing's sovereignty claims over Taiwan, but it did take the military off the front line of efforts to 'liberate' the island. Even so, Beijing has used Taiwan's military power as a reason to modernise its own forces - forces Beijing still uses to deter independence moves on the island. Xu's announcement on January 1, 1979, was followed later that day by the National People's Congress in Beijing issuing a 'Letter to Taiwan Compatriots', calling on both sides to establish 'three links': in trade, postal services and transport. It also suggested that the Chinese Communist Party and its Taiwanese counterpart, the KMT, should advance 'four exchanges': in economics, culture, technology and sport. Two years later, then NPC Standing Committee chairman Ye Jianying delivered his idea of 'nine points of principles' for 'peaceful reunification'. Ye also introduced the basic idea of the 'one country, two systems' approach, later expanded by paramount leader Deng Xiaoping . Andy Chang Wu-yue, director of the Institute of China Studies at Tamkang University in Taipei, said the end of direct cross-strait military confrontation pointed to the PLA's diminished role in cross-strait affairs since 1979. 'Since 1979, the PLA's mission has changed from liberating the island by armed might to a peaceful offensive,' he said. '[It] has changed from attacking Taiwan to punishing pro-Taiwan-independence supporters since the mainland opened up.' But the PLA's mission of reunifying Taiwan with the mainland was just as strong as ever, mainland military experts said. 'The PLA has never stopped upgrading its armed forces and weapons, even though the prospects of an exchange of fire with Taiwan have become slim,' one Shanghai-based expert military said. The US Department of Defence says the PLA has matched Taiwan's 340,000-strong army by deploying 400,000 personnel and over 300 advanced fighter jets and 50 submarines in the three military commands at the front line - Nanjing , Jinan and Guangzhou. The Shanghai military expert said the rising independence sentiment in Taiwan had provoked an arms race between Beijing and Taipei, with the Second Artillery Corps, the mainland's strategic and tactical missile group, being given virtually any resources it needs for its development since the 1990s. 'The development of the PLA's submarine unit is aimed at attacking Taiwan some day, while the Second Artillery Corps has middle and long-range missiles targeted at the US and Japan, countries that would be involved in a cross-strait crisis,' he said. When pro-independence leader Lee Teng-hui was re-elected Taiwan's president in 1996 and his successor, Chen Shui-bian, came to power in 2000, the submarine and missile corps were deployed to the Fujian coast for a series of drills that were Beijing's warnings to Mr Lee and Mr Chen. Since 1996, Beijing has boosted the number of missiles along the Fujian coast aimed at Taiwan from 10 to 1,328. But the missile tests and drills had the opposite of Beijing's intended effect, serving only to increase public support for Mr Lee and Mr Chen. 'In the Deng Xiaoping and Jiang Zemin eras, Beijing's top leaders all believed that cross-strait problems should be solved by arms,' the Shanghai expert said. 'But that dominant mindset was put aside when pragmatic President Hu Jintao came to office in 2003, to protect the hard-won achievements of economic reform in coastal areas.' But Mr Hu did not abandon military options altogether. In 2005, the NPC passed Mr Hu's 'anti-secession law', which declared that it was legitimate for the mainland to use 'non-peaceful means' to respond to a declaration of Taiwanese independence. 'The passing of the anti-secession law gave the PLA the legal right to intervene in cross-strait affairs, and also retained the military as the last trump card for Beijing to play to prevent Taiwan independence,' Tamkang University professor Alexander Huang Chieh-cheng said. 'In fact, Taiwan affairs have given the PLA the perfect excuse to push ahead with modernisation, including increasing the defence budget, buying advanced weapons from overseas, developing homegrown weapons and upgrading military hardware.'