In some parts of the country, particularly smaller regions, "daimyōs" and samurai were more or less identical, since "daimyōs" might be trained as samurai, and samurai might act as local lords. Otherwise, the largely inflexible nature of this social stratification system unleashed disruptive forces over time. Taxes on the peasantry were set at fixed amounts which did not account for inflation or other changes in monetary value. As a result, the tax revenues collected by the samurai landowners were worth less and less over time. This often led to numerous confrontations between noble but impoverished samurai and well-to-do peasants. None, however, proved compelling enough to seriously challenge the established order until the arrival of foreign powers.