The first line refers to the northeast and coastal areas, and the second line refers to the vast area between the first and third lines. The third line is divided into "big third line" and "small third line", and the big third line involves the above 13 provinces and regions. The Small Third Line refers to the combat readiness construction in the first-and second-tier areas that focus on national defense within their jurisdiction according to the requirements and planning of the central authorities.

From 65438 to 0964, the CPC Central Committee made a strategic decision and deployment of "doing a good job in strategic layout and strengthening the third-line construction", and China carried out large-scale economic construction in the southwest and northwest inland areas, which was called the third-line construction in history. The so-called "third line" means that Chairman Mao divided the whole country into the first, second and third lines according to the strategic needs of China at that time, and the third line area is the strategic rear area of the country (referred to as the third line).

The third-tier areas include all or most of Sichuan, Guizhou, Yunnan, Shaanxi, Gansu, Qinghai and Ningxia, western areas of Henan, Hubei, Hunan and Shanxi, northern Guangdong and northwestern Guangxi.

Detailed introduction

Third-line construction is a large-scale capital construction with combat readiness as the guiding ideology and basic industries, national defense science and technology industries and transportation as the goals. After three five-year plans, the peak investment was 205.2 billion yuan, with more than 4 million people, and construction projects were arranged 1 100.

From the construction period, it lasted from 1964 to 1979 for 15 years, and from the adjustment period, it was initially adjusted for 4 years, from 1979 to 1983 to 2003.