Introduction:
The Delhi Sultanate, established in the 13th century, faced significant challenges in controlling the hinterland initially. Several factors contributed to their inability to establish control over the entire region.

1. Limited Military and Administrative Resources:
- The rulers of the Delhi Sultanate had limited military and administrative resources to exert control over a vast and diverse hinterland.
- They primarily relied on the existing administrative infrastructure, which was not designed to govern such a large territory.
- Lack of sufficient manpower and resources made it difficult for the Sultanate to enforce its authority effectively.

2. Geographical Barriers:
- The hinterland of the Delhi Sultanate was characterized by diverse geographical features such as dense forests, rugged terrains, and riverine systems.
- These geographical barriers made it challenging for the Sultanate to establish a strong presence and control over remote areas.
- The lack of proper transportation and communication infrastructure further hindered their efforts to control the hinterland.

3. Resistance from Local Rulers and Tribes:
- The rulers of the Delhi Sultanate faced resistance from various local rulers and tribal communities in the hinterland.
- Many regional rulers and tribal chiefs were reluctant to submit to the authority of the Delhi Sultanate and preferred to maintain their independence.
- The Sultanate struggled to suppress rebellions and uprisings, which further undermined their control over the hinterland.

4. Cultural and Linguistic Diversity:
- The hinterland of the Delhi Sultanate was inhabited by diverse ethnic and linguistic groups with their own distinct cultural identities.
- The Sultanate's attempts to impose their administrative and cultural practices often faced resistance from the local population.
- The rulers failed to effectively integrate these diverse communities into the Sultanate's administrative system, making it difficult to establish control.

5. Economic Factors:
- The hinterland of the Delhi Sultanate was economically self-sufficient, with thriving agricultural and trading activities.
- The Sultanate's attempts to extract resources and impose heavy taxes often met with resistance from the local population.
- The economic prosperity of the hinterland allowed local rulers and communities to maintain a certain level of autonomy, undermining the Sultanate's control.

Conclusion:
The rulers of the Delhi Sultanate initially failed to control the hinterland due to limited resources, geographical barriers, resistance from local rulers and tribes, cultural diversity, and economic factors. These challenges made it difficult for the Sultanate to establish a strong and centralized authority over the entire region. Over time, however, the Sultanate made efforts to overcome these obstacles and gradually extended their control over the hinterland.