Given the following context:

On the battlefield, the king's commanders led the troops. The empire's war strategy rarely involved massive invasions; more often it employed small scale methods such as attacking and destroying individual forts. The empire was among the first in India to use long range artillery commonly manned by foreign gunners (those from present day Turkmenistan were considered the best). Army troops were of two types: The king's personal army directly recruited by the empire and the feudal army under each feudatory. King Krishnadevaraya's personal army consisted of 100,000 infantry, 20,000 cavalrymen and over 900 elephants. This number was only a part of the army numbering over 1.1 million soldiers, a figure that varied as an army of two million has also been recorded along with the existence of a navy as evidenced by the use of the term Navigadaprabhu (commander of the navy). The army recruited from all classes of society (supported by the collection of additional feudal tributes from feudatory rulers), and consisted of archers and musketeers wearing quilted tunics, shieldmen with swords and poignards in their girdles, and soldiers carrying shields so large that no armour was necessary. The horses and elephants were fully armoured and the elephants had knives fastened to their tusks to do maximum damage in battle.The capital city was completely dependent on the water supply systems constructed to channel and store water, ensuring a consistent supply throughout the year. The remains of these hydraulic systems have given historians a picture of the prevailing surface water distribution methods in use at that time in the semiarid regions of South India. Contemporary records and notes of foreign travelers describe how huge tanks were constructed by labourers. Excavations have uncovered the remains of a well-connected water distribution system existing solely within the royal enclosure and the large temple complexes (suggesting it was for the exclusive use of royalty, and for special ceremonies) with sophisticated channels...

answer the following question:

What employed a war strategy method such as attacking and destroying individual forts? 

The empire