What significant health event occurred to Lenin on January 21, 1924?

On January 21, 1924, Vladimir Lenin suffered what is recognized as a significant health event that marked the last phase of his life, specifically a third stroke. This stroke led to a rapid decline in his health and was critical because it severely affected his ability to participate in political affairs. Lenin had already experienced previous strokes, which had progressively incapacitated him and made it difficult for him to exert control over the Soviet state, ultimately paving the way for a power struggle among his colleagues. The occurrence of this third stroke is essential in understanding the dynamics of Soviet leadership during this period and how it influenced the subsequent rise of figures like Joseph Stalin, who maneuvered politically in the absence of Lenin's guidance.