The document known as Lenin’s political testament was in fact a series of short letters, written to the Congress of Soviets over the course of a week in December 1922. In these letters, Lenin expressed concern about a potential split in the Bolshevik Central Committee, chiefly because of the rivalry and animosity between Stalin and Trotsky:

“I would urge strongly that at this Congress a number of changes are made in our political structure. I want to tell you of the considerations to which I attach most importance.

At the head of the list, I set an increase in the number of Central Committee members, to a few dozen or even a hundred. It is my opinion that without this reform our Central Committee would be in great danger if the course of events were not quite favourable for us… I think it must be done in order to raise the prestige of the Central Committee, to do a thorough job of improving our administrative machinery and to prevent conflicts between small sections of the Central Committee from acquiring excessive importance…

By stability of the Central Committee, of which I spoke above, I mean measure against a split, as far as such measures can at all be taken. For, of course, the white guard in Russkaya Mysl (it seems to have been S.S. Oldenburg) was right when, first, in the white guards’ game against Soviet Russia he banked on a split in our Party, and when, secondly, he banked on grave differences in our Party to cause that split.

I have in mind stability as a guarantee against a split in the immediate future, and I intend to deal here with a few ideas concerning personal qualities.

I think that from this standpoint the prime factors in the question of stability are such members of the Central Committee as Stalin and Trotsky. I think relations between them make up the greater part of the danger of a split, which could be avoided. [This could be avoided] by increasing the number of C.C. members to 50 or 100.

Comrade Stalin, having become Secretary-General, has unlimited authority concentrated in his hands – and I am not sure whether he will always be capable of using that authority with sufficient caution. Comrade Trotsky, on the other hand, as his struggle against the Central Committee on the question of the People’s Commissariat of Communications, has already proved [his] outstanding ability. He is personally perhaps the most capable man in the present Central Committee – but he has displayed excessive self-confidence and preoccupation with the purely administrative side of the work.

These two qualities of the two outstanding leaders of the present Central Committee can inadvertently lead to a split, and if our Party does not take steps to avert this, the split may come unexpectedly.”

In an additional letter written in January 1923, Lenin clarified on his assessment of Stalin:

“Stalin is too rude and this defect, although quite tolerable in our midst and in dealing among us Communists, becomes intolerable in a Secretary-General. That is why I suggest that the comrades think about a way of removing Stalin from that post and appointing another man in his stead who in all other respects differs from Comrade Stalin in having only one advantage, namely, that of being more tolerant, more loyal, more polite and more considerate to the comrades, less capricious, etc. This circumstance may appear to be a negligible detail. But I think that from the standpoint of safeguards against a split and from the standpoint of what I wrote above about the relationship between Stalin and Trotsky it is not a [minor] detail, but it is a detail which can assume decisive importance.”