One of the most striking features of modern history has been the tremendous number of revolutionary upheavals; equally striking, however, is the fact that most of these revolutions have failed to overthrow capitalist or have fallen victim to Stalinism.
Why has this period of great possibilities produced so many defeats and disappointments? According to Trotsky's analysis in the Transitional Program, the betrayals of the traditional workers' parties - the reformist Socialist parties and the Stalinized Communist parties - left the masses leaderless and demoralized; at the same time the genuine revolutionary forces were too small to the lead the insurgent masses to the conquest of power.
The key problem that Trotsky deals with in the Transitional Program is how to bridge this gap between the overripe historical conditions and the relative weakness of the revolutionary vanguard. Trotsky saw the solution to this problem in mobilizing people around demands suited to their immediate needs and levels of consciousness, but pointing towards the conquest of power and the elimination of the root cause of their oppression, capitalism.