After the death of Harshvardhan in 648 CE,his capital, the city of Kannauj, remained the symbol of imperial power and was coveted by three powerful dynasties- the gurjara Pratiharas of Western India, The Rashtrakutas of Deccan, and the Palas of Bengal. Kannauj was of great strategic importance, as whoever controlled it also controlled the rich and fertile Ganga plains.The city was so battered by two centuries of conflict that it never rose again and this state of constant warfare also weakened the three dynasties.
Later,, the historians, called this as tripartite struggle.

It was called a political history because the three dynasties were at constant war to control that area after Harshvardhan 's death.

The Period After Harshavardhan's Death: A Period of Political History

After Harshavardhan's death, the period that followed was marked by significant political changes and developments. This period is considered a crucial phase in Indian history, particularly in the context of the emergence of new kings and kingdoms. Let's delve into the details of why this period is regarded as a period of political history.

1. Fragmentation of Power:
- Harshavardhan was a powerful ruler who held a vast empire, extending from present-day Punjab to Bihar.
- However, after his death, the empire faced internal conflicts and power struggles among his successors.
- This fragmentation of power resulted in the disintegration of the unified empire into several smaller kingdoms.
- The emergence of these new kings and kingdoms marked a significant shift in the political landscape of the Indian subcontinent.

2. Rise of Regional Powers:
- With the disintegration of Harshavardhan's empire, regional powers began to assert themselves.
- Various local rulers and dynasties, such as the Pallavas, Chalukyas, and Pandyas, gained prominence in different regions.
- These regional powers often engaged in conflicts and alliances with each other, leading to the formation of new kingdoms.

3. Dynastic Successions:
- The period after Harshavardhan's death witnessed frequent changes in dynastic successions.
- Many rulers and leaders rose to power through conquests or by challenging existing dynasties.
- These changes in power dynamics contributed to the political instability of the time.

4. Political Alliances and Conflicts:
- The period also saw the formation of political alliances and conflicts between different kingdoms.
- These alliances were often forged to counter external threats or to gain more power.
- The political landscape was characterized by a constant struggle for supremacy among these kingdoms.

5. Cultural and Economic Impact:
- The political changes during this period also had significant cultural and economic implications.
- The rise of new kings and kingdoms led to the spread of different regional cultures, languages, and traditions.
- Trade and commerce flourished as these kingdoms developed their own economic systems and engaged in inter-regional trade.

Conclusion:
The period after Harshavardhan's death is considered a period of political history due to the fragmentation of power, the rise of regional powers, changes in dynastic successions, political alliances and conflicts, and their cultural and economic impact. These political developments shaped the course of Indian history and set the stage for the subsequent rise and fall of various kingdoms and empires.