Why did Japan need to rebuild its economy following world war 2

Japan had already developed to a high level in heavy manufacturing, steel making, ship building, heavy chemicals and vehicle manufacturing prior to WW2 based on a policy of a partnership between business and government with a high degree of government direction and assistance with investment. With the destruction by bombing of much of Japans industrial infrastructure the Japanese took the opportunity to invest in new state of the art manufacturing facilities. As a result Japan spent a higher percentage of its GDP on investment than countries like the US and the UK and Japanese consumers accepted that sacrifices had to be made in the medium term to rebuild the economy and accepted a lower standard of living in the years following the war. A system of training and apprenticeships in industry was also highly developed and the university system had close links to industry to provide the correct level of trained management personnel. The Japanese system of a 'job for life' plus a comprehensive structured system of training and development of managers ensured that knowledge was developed and transmitted in a way superior to that in Western companies. In a large Japanese company a manager will do a 3 year stint in a particular position at home or abroad and receive close training and monitoring by his immediate manager who he will probably take over from. The result of this system is that 3 levels of management have a detailed knowledge of the job etc at any one time. In the West managers move between companies a lot more leading to a loss of accumulated knowledge to that company.