In the relations of the seigniorial elements and the monarchy this was a critical period for the latter, deciding as a result of the virtual, though not at the time apparent, victory of the kings that Castile was to become a power in the world. For that very reason the evolution of political institutions in this era was important, for on the development of monarchy depended the conquest of America, but they were also important because the institutions which were set up in the new world had noteworthy antecedents at this time. Influenced largely by the principles of the Roman law the kings aspired to absolute monarchy in a centralized state, with a view to overcoming the social and political strife resulting from the diffusion of power inherent in the seigniorial system. Their most dangerous enemies were the nobles, whose spirit of independence and self-esteem and whose vast wealth in lands and fighting men made them a powerful factor in themselves. They were yet stronger because the kings had to depend on them for military service since there was no large standing army, and because they in a measure developed a class consciousness in opposition to absolutism, becoming a nobility rather than remaining a mere aggregation of nobles. While the seigniorial ideal was not lacking in the towns, they were not nearly so dangerous to the monarchy, because they were usually as hostile to the nobility as the kings were. Often, however, they fought against the kings, or exacted concessions for their services. The task for the fulfilment of royal ideals was therefore a difficult one, requiring a sagacious type of monarch, such as in fact rarely appeared in the period. Circumstances fought better than the kings, and nowhere does this show forth more clearly than in a review of the political institutions of the era. [Sidenote: Internal decline in the power of the nobles.]