Excerpts from Petras thesis:

Imperialism, its character, means and ends has changed over time and place.

Under pressure from nationalist and socialist anti-imperialist movements and regimes, colonial structured empires gave way to new nationalist regimes. Some of which restructured their economies, diversifying their productive systems and trading partners.

Historically, economic imperialism (EI) resorted to military intervention to overthrow anti-imperialist regimes and secure collaborator political clients. Subsequently, EI frequently established military bases and training and advisory missions to repress resistance movements and to secure a local military officialdom responsive to the imperial power. The purpose was to secure economic resources and a docile labor force, in order to maximize economic returns