It then continues by forecasting the positions of China, Japan, the European Economic Community (EEC), the Soviet Union and the United States through the end of the 20th century.

[2] Throughout the book he reiterates his early statement (page 71): "Military and naval endeavors may not always have been the raison d'être of the new nations-states, but it certainly was their most expensive and pressing activity", and it remains such until the power's decline.

[3] Kennedy states his theory in the second paragraph of the introduction as follows: The "military conflict" referred to in the book's subtitle is therefore always examined in the context of "economic change".

The triumph of any one Great Power in this period, or the collapse of another, has usually been the consequence of lengthy fighting by its armed forces; but it has also been the consequences of the more or less efficient utilization of the state's productive economic resources in wartime, and, further in the background, of the way in which that state's economy had been rising or falling, relative to the other leading nations, in the decades preceding the actual conflict.

Relative shares of world manufacturing output (also first appearing on page 149) are used to estimate the peaks and troughs of power for major states.

Kennedy also emphasizes productivity increase, based on systematic interventions, which led to economic growth and prosperity for great powers in the 20th century.

Kennedy predicts the rise of China, stating that if kept up, its economic development would change the country in decades and it would become a great power.

[6]: 141  He highlights the precedent of the Four Modernizations in Deng Xiaoping's plans for China—agriculture, industry, science and military—de-emphasizing military, while the United States and Soviet Union are emphasizing it.

From the Civil War to the first half of the 20th century, the United States' economy benefited from high agricultural production, plentiful raw materials, technological advancements and financial inflows.

[12] The United States has the typical problems of a great power, which include balancing guns and butter and investments for economic growth.

[16] Kennedy's advice is as follows: The task facing American statesmen over the next decades, therefore, is to recognize that broad trends are under way, and that there is a need to "manage" affairs so that the relative erosion of the United States' position takes place slowly and smoothly, and is not accelerated by policies which bring merely short-term advantage but longer-term disadvantage.