Club Dutt

This single sentence fragment really sums up the cause of the growth of imperialism

His own [capitalist's] private consumption counts as a robbery committed against the accumulation of his capital, just as, in double-entry book-keeping, the private expenditure of the capitalist is placed on the debit side of his account against his capital. Accumulation is the conquest of social wealth. It is the extension of the area of exploited human material and, at the same time, the extension of the direct and indirect sway of the capitalist. [Martin Luther excerpt continues here]

Here again is the core logic, demonstrating that

1. Domestic consumption even by the capitalist himself is not enough
2. The world scope of capital looms at us already in the 1800s