I think that Stalin was successful in his centralization of power because he simply removed those who were seen as impediments to his power. Stalin was fairly direct in his ideas that when Lenin left, he and his own sense of self would embody the nation and the political movement of Communism. This made Stalin highly successful in centralizing power. In this, Stalin would centralize power by eliminating competitors such as Sergei Kirov, Leon Trotsky, and using the idea of the purges and his declaration of "public enemies" that made it near impossible to pose a significant and credible opposition to Stalin. This makes the centrality of power for him something that is almost guaranteed. Stalin was able to centralize power by strengthening the executive, in particular enhancing Soviet secret service and intelligence. Stalin centralized power by using it as a way to ensure that he was able to gather intelligence about people he perceived as "enemies" or even opponents, ensuring that he knew their next move before it was carried out. In doing so, Stalin was able to make power synonymous with his own being, centralizing it and ensuring that its focus was consistent with what he wanted and desired.