The People's Liberation Army's relief operation in Sichuan has exposed weaknesses in the world's largest fighting force, experts say. The military played the most critical role in the rescue mission - with most roads and bridges in the area destroyed, many of the hardest-hit areas could only be reached by soldiers. More than 140,000 military personnel have been mobilised, taken from all sectors of the force - from paratroopers to the strategic-missile divisions. The disaster put the PLA, which has not fought a war for almost three decades, to a severe and highly visible test. Initially, the PLA tried twice - and failed - to land a helicopter at the epicentre. An attempt to drop paratroopers into the epicentre was also abandoned, so the first batch of rescue troops had to enter on foot. The PLA then air-dropped equipment, food and water to soldiers and refugees in the disaster zone. While the scale of the airlift operations was hailed by Xinhua as 'unprecedented', it was nowhere close to the capability demonstrated by the US military in other parts of the world. Mainland media said about 100 military and civilian helicopters were deployed. But many ground troops criticised the airlift missions as ineffective. 'I did not see any helicopter in this area. I only know it's our soldiers who carried food and water to people in remote villages,' said Commander Liu Pu, the PLA co-ordinator in Qingchuan county. The commander also said many relief goods were air-dropped in the wrong places, such as unpopulated mountain areas. Soldiers had to spend hours retrieving them. Other supplies were dropped in areas that were simply out of reach. A Shanghai-based military source said the arms embargo imposed on China, combined with an inadequate budget, meant the force was poorly equipped. 'We still have no capability to produce advanced military helicopters and had to rely on imports,' he said. 'The most advanced helicopters we deployed [in the rescue operation] are US-made Black Hawks,' which were developed in the early 1970s. He also blamed poor training of PLA pilots. 'Because of an insufficient budget, many pilots can only fly once a year,' he said. 'The mountainous terrain in Sichuan made an air-drop operation very difficult. Inexperienced pilots dared not fly too low. That is why they had to drop material from higher up, and that explains why the landings were not accurate.' Another problem was poor communication among the different units. PLA soldiers are supposed to use special military telephone lines for security purposes, but the communication devices given to the various units were not compatible. 'It is very difficult to co-ordinate with different troops in areas where there are no civilian landlines or cellphone signals,' the commander said. The troops found that even in areas with landlines, they could not get through. The commander had a satellite phone to allow him to contact the command centre in an emergency. But on many occasions civilian disaster-relief officials borrowed it to make calls. The communication problem extended to contacting civilian officials. Wang Taiping, commander-in-chief in the Guangyuan division of the Sichuan Military Region, tried to make an important call to a vice-mayor but only got a busy signal. 'Is it true this guy was supposed to co-ordinate the overall military and civilian rescue efforts in this area?' Mr Wang was heard shouting at his secretary after trying in vain for 20 minutes. Soldiers who arrived on the second and third days after the earthquake also found supplies of food and water, which were supposed to arrive at the area as they did, had not arrived. The supply problem was not resolved until the fourth day. Military trucks were seen stuck in mud or even having crashed on the winding roads to Qingchuan. One military driver complained that people from flat areas found driving on mountain roads too difficult. Hong Kong-based military analyst Andrei Chang said the relief mission had exposed weaknesses in the PLA. The force was struggling to carry out operations that would be standard during modern warfare. 'The disaster areas are like real battlefields. Good co-ordination, co-operation among different forces is necessary in today's battlefields. But the PLA just couldn't do it.'