When China's first large-scale military parade in years rolls through Beijing on Thursday, the world will be pondering what isn't on display. Its military brass are keen to showcase the domestically produced fighter planes, tanks and missiles, but the focus of security analysts and scholars lies elsewhere. It is the less visible assets - thousands of kilometres of fibre optic cable, submarines able to carry nuclear missiles deep into the western Pacific and Indian Oceans, research skills and facilities - that tax the minds of those scrutinising the military build-up. Even US conservatives acknowledge that it is natural for China to expand and modernise its armed forces, but the extent of its capabilities - along with Beijing's intentions - face increasing external scrutiny. How far has the People's Liberation Army come after 15 years of rapid modernisation? Precisely what can it do? How would it put it all together in a conflict? Defence Minister General Liang Guanglie sparked fresh debate in a rare interview posted on the ministry's website last week. The mainland's military, he said, now possessed most of the sophisticated weapons systems found in Western arsenals. 'This is an extraordinary achievement that speaks to the level of our military's modernisation and the huge change in our country's technological strength,' he said. Such remarks go beyond the usual rhetoric from Beijing spokesmen, who dismiss as a fallacy the suggestion China's military poses any threat. The remarks are more in line with President Hu Jintao's doctrine of building a modern military commensurate with China's international stature and interests. As the world's third-biggest economy, and one with a thirst for natural resources and with investments spanning the globe, these interests are growing. They include the need to defend shipping lanes and pipelines and involve arenas far beyond the Taiwan-invasion scenarios that previously dominated military thinking. Gary Li, a researcher at the London-based International Institute of Strategic Studies, said a careful reading of Liang's remarks suggested he was talking about China's goals as much as the recent past. 'I think Liang's remarks ultimately speak to China's ambitions ... leaders like him know there is still so much to be done and so many gaps to be filled,' Li said. Talk to analysts and military attach?s at Asian, Australian, European and US think tanks and embassies and it becomes clear that for virtually every concern about China's military expansion there is a counter argument that the PLA still faces many struggles if it is to fully modernise by mid-century. Take, for example, the J-10 fighter jet - the product of a two-decade-long effort to create a state-of-the-art multi-role fighter comparable with those produced by the US, France and Russia. J-10s are expected to feature prominently in Thursday's parade. Yet for years, J-10 prototypes were powered by Russian engines. China recently produced its own engine, but its reliability is in doubt after two recent accidents, foreign military observers say. 'China is catching up, but it is still a long way off when it comes to the hard engineering of producing the most advanced jet engine and components that can withstand all the stresses involved,' said one Western military attach?. 'Russia and the West have the benefits of 70 years of hard research and development by fully functioning military-industrial complexes ... That is virtually impossible to replicate in short order.' Then there are the submarines. The navy is at the core of modernisation efforts - the military wants to be able to project China's power across oceans with a fleet of aircraft carriers. Submarines are crucial to that goal. Independent estimates suggest China has more than 60 operational submarines and will soon have the biggest fleet. At least two are believed to be Jin-class boats capable of carrying nuclear missiles. But though the newest, they are still considered noisy and half a generation behind the best Russian and US technology. Still, PLA subs are patrolling more often and going further. They are regularly detected out in the Pacific, beyond Japan and towards Guam. A new deep-water base in Hainan extends their reach. Far from merely raising China's presence in the disputed South China Sea, this base allows the secret launch of missions into both the Indian and Pacific Oceans. Other nations are scrambling to catch up. 'I worry we are going to see a greatly enhanced risk of conflict and misunderstandings given all this rising submarine activity in East Asia,' said Sam Bateman, a senior fellow at the Institute of Defence and Strategic Studies in Singapore. 'That in itself would be a big test of just how far China has come in terms of training and command ... by their nature, submarines often have to spend long periods completely out of reach of communications.' Submarines play a key role in the maintenance of one of China's military successes - its nuclear deterrent. Thursday's parade is expected to feature giant trucks carrying intercontinental ballistic missiles. Once, China's nuclear warheads were kept on missiles in underground silos - a psychological rather than practical second-strike deterrent. (Since its first successful atomic-bomb test in 1964, China has, uniquely, maintained a 'no first use' policy.) The combination of submarines and road-mobile missiles adds greatly to the difficulties facing any nation contemplating a nuclear attack on China. Silos can be detected and destroyed, but submarines and trucks can be shifted constantly. The PLA's range of conventional missiles has also increased. And it has made advances in the fields of cyberwarfare, command and control and intelligence. China's ability to cripple an enemy's institutions via modern communications is widely considered to be as advanced as any nation's. Cyberwarfare can be seen as part of the PLA's growing commitment to asymmetric warfare - the ability to strike at a larger opponent through an array of novel, low-visibility means. It also reflects broader efforts to integrate military and civilian infrastructure for maximum benefit during wartime. The military field that experts call C4-ISR (command and control, computers and communications plus intelligence, surveillance and reconnaissance) is vital to co-ordinating a modern, diverse and highly mobile military. It involves exploiting technology to the full - from sensors carried by individual soldiers to electromagnetic devices able to thwart enemy communications. C4-ISR is at the cutting edge of military planning. Debate is raging about how far China has come. James Mulvenon, a researcher on military-intelligence in Washington, said China had made great strides in this arena. 'There has been a very impressive gain in the breadth and depth of their capabilities that is comparable to anything out there,' said Mulvenon, formerly a researcher on China for the Rand Corporation set up by the US military but which is now a non-profit research institution. For instance, China aims to have its own global positioning system in place within 10 years, ending its reliance on US coverage. US forces now approach the Chinese coastline and airspace with considerable caution. However, China still faces limitations in research and development, logistics and military diplomacy. Traditionally much of China's military technology has come from Russia. Perennial friction and suspicions of theft and espionage now limit this flow, making more urgent China's need for a military-industrial complex of its own. Its work on jet engines and submarine propulsion systems highlights the struggle. The Pentagon's annual survey of the Chinese military notes that research and development spending is not part of the official defence budget, which this year is US$70.3 billion. Tim Huxley, executive director of the International Institute for Strategic Studies (IISS) in Asia, believes progress will depend on the mainland's economic performance. Military logistics is still a problem for PLA strategists. It lacks the heavy-lift aircraft vital for large-scale troop movements. At sea, regional analysts believe China lacks refuelling and resupply vessels. It also lacks anti-mine ships - vessels other navies consider standard equipment. In terms of organisation, PLA planners are believed to be struggling to break down army divisions into smaller, more flexible brigades, in keeping with modern thinking. As for military diplomacy, China is still finding its way. The PLA's contribution of 13,000 troops to UN peace-keeping operations, and the participation of PLA ships in anti-piracy patrols off Somalia, are only first steps, Western and Asian diplomats believe. The fulfilment of China's naval ambitions will hinge on extensive access to third-country ports of the sort Western navies enjoy. Expect more attention to be paid to transparency and diplomacy in coming years. For all the questions about its hardware and software, perhaps the biggest challenges faced by China's military are political. Question marks remain about whether its traditionally rigid command structures can promote the flexibility, creativity and initiative the modern warrior needs. Then there is the nagging doubt about how Beijing's leaders will manage the fast-evolving, ultra-modern force they hope to have created within 30 years. Li at the IISS said he had noted increasing efforts to ensure the PLA remains politically aligned with the aspirations of the Communist Party leadership. 'I think this will be a priority as the military modernises,' he said. Mulvenon says the single biggest challenge is potential friction as military leaders seek to test their new capabilities in ways that worry the political leaders. 'They have reached the point where they have capabilities and are starting to rub up against political limits ... Maybe they will want to test Japan or US forces in a way that makes the leadership uncomfortable. Managing those limits is going to be difficult. I think that is a worry inside and outside China,' he said. For every item of military hardware that rolls across Tiananmen Square on Thursday, there are many more questions taxing China's neighbours. The PLA may well be on its way, but it isn't there quite yet.