The USSR was the world’s single greatest anti-imperialist power throughout its history. Lenin would know about imperialism, considering he wrote Imperialism, the Highest Stage of Capitalism, the single most important Marxist work on analyzing capitalism’s imperialist stage. In this quote, he is addressing the Kautsky-ites that tried to disentangle imperialism from capitalism, written here more clearly:

It is clear why imperialism is moribund capitalism, capitalism in transition to socialism: monopoly, which grows out of capitalism, is already dying capitalism, the beginning of its transition to socialism. The tremendous socialisation of labour by imperialism (what its apologists — the bourgeois economists — call “interlocking”) produces the same result.

Advancing this definition of imperialism brings us into complete contradiction to K. Kautsky, who refuses to regard imperialism as a “phase of capitalism” and defines it as a policy “preferred” by finance capital, a tendency of “industrial” countries to annex “agrarian” countries.

Kautsky’s definition is thoroughly false from the theoretical standpoint. What distinguishes imperialism is the rule not of industrial capital, but of finance capital, the striving to annex not agrarian countries, particularly, but every kind of country. Kautsky divorces imperialist politics from imperialist economics, he divorces monopoly in politics from monopoly in economics in order to pave the way for his vulgar bourgeois reformism, such as “disarmament,” “ultraimperialism” and similar nonsense. The whole purpose and significance of this theoretical falsity is to obscure the most profound contradictions of imperialism and thus justify the theory of “unity” with the apologists of imperialism, the outright social-chauvinists and opportunists.

• Imperialism and the Split in Socialism