Write a detailed long answer on the Kushanas.

The Kushanas were a dynasty that ruled over parts of Central Asia and South Asia during the first to the third centuries AD. They were one of the five tribes of the Yuezhi confederation, a nomadic group from Central Asia. The Kushanas are known for their significant contributions to art, religion, and administration, which had a profound impact on the regions they ruled.

The Kushanas were initially part of the Yuezhi confederation in Central Asia. After a defeat by the Xiongnu, another nomadic group, the Yuezhi migrated towards the south and west. Around the first century AD, one of the five tribes of the Yuezhi, the Kushanas, established a kingdom in Bactria, present-day Afghanistan. The Kushanas gradually expanded their kingdom to include parts of Central Asia, northern India, and parts of China's western regions.

The Kushanas are perhaps best known for their king, Kanishka, who is considered one of the greatest Buddhist kings. Kanishka came to the throne in the second century AD and expanded the Kushana Empire to its greatest extent. He is known for his patronage of Buddhism and the arts. Under his rule, the Gandhara School of Art flourished, which combined Greek, Persian, and Indian influences. Kanishka also convened a great Buddhist council in Kashmir, which led to the development of Mahayana Buddhism.

The Kushanas were also known for their administrative skills. They controlled a vast and diverse empire, and to do so, they adopted a policy of local autonomy, allowing local rulers to maintain their positions in return for loyalty. This policy helped maintain stability and prosperity in the empire.

The Kushanas also had a significant impact on trade and economy. They controlled the Silk Road, a major trade route connecting China with the Mediterranean. This control allowed them to facilitate and benefit from trade between different parts of Asia and Europe.

In terms of religion, the Kushanas were tolerant and syncretic. While they patronized Buddhism, they also incorporated elements of other religions into their practices. Coins from the Kushana period depict a variety of deities from Greek, Hindu, and Zoroastrian traditions, reflecting the diverse religious influences in their empire.

The Kushana Empire began to decline in the third century AD, with parts of the empire breaking away and the Sassanids and Gupta Empire encroaching on their territory. Despite their decline, the Kushanas left a lasting legacy, particularly in the fields of art and religion. Their rule marked a significant period in the history of Central and South Asia, with impacts that can still be seen today.