Final answer:
The Vijayanagara Empire fought against the Deccan Sultanates for control of fertile river valleys and faced European powers like the Portuguese for control over resources from lucrative overseas trade, leading to complex geopolitical dynamics in the Indian subcontinent.
Step-by-step explanation:
The Vijayanagara Empire faced various competitors for different strategic interests over the course of its history. For the control of fertile river valleys, they contended with adjoining kingdoms and Sultanates such as those rulers of the Deccan Sultanates. These regions were crucial for agriculture and sustaining the population.
When it came to resources generated by lucrative overseas trade, the competition extended to European powers along with other regional sultans. The Portuguese were among the first Europeans to attempt to establish trading posts in India, seeking to control wealth through overseas trade. They were followed by English and French forces, which meant the Vijayanagara rulers not only had internal conflicts with local Indian realms but also with burgeoning European powers.
The rivalry over these valuable territories and trade routes spurred massive military and political maneuvering. This shaped the geopolitics of the Indian subcontinent, eventually paving the way for British consolidation of power, taking advantage of the waning might of the Mughal and Maratha forces.