Explanations:To understand the context of Muhammad-bin Tughlaq's military strategy for securing the northern frontiers of the Sultanate, it is essential to consider the geographical and strategic importance of the regions involved. The Sultanate of Delhi, under Muhammad-bin Tughlaq, faced significant threats from the north, particularly from Central Asian invaders and other regional powers. To counter these threats, Tughlaq focused on securing key regions that acted as natural barriers and strategic strongholds.
Himachal Pradesh and Kangra were two such regions. Himachal Pradesh, located in the northern part of the Indian subcontinent, is characterized by its mountainous terrain, which provided a natural defense against invasions. The rugged landscape made it difficult for invaders to penetrate the Sultanate's territory, thus serving as a crucial buffer zone. Kangra, a region in the western part of Himachal Pradesh, was also strategically important due to its location and the presence of the Kangra Fort, which was a significant military stronghold.
By securing these regions, Muhammad-bin Tughlaq aimed to create a strong defensive line against potential invasions from the north. The fortifications and military presence in these areas helped to deter and repel invaders, thereby ensuring the stability and security of the Sultanate's northern frontiers. The strategic importance of these regions is well-documented in historical records and is a key aspect of the Sultanate's military and administrative policies.
It is important to note that while other regions were also part of the Sultanate's defense strategy, Himachal Pradesh and Kangra were particularly significant due to their geographical features and historical importance. Therefore, the correct answer is that Muhammad-bin Tughlaq sent forces to secure both Himachal Pradesh and Kangra, making option D the correct choice.