In the history of Magadha, which ruler is credited with choosing Pataliputra as the capital city for the first time?

Introduction / Context:
Pataliputra (near modern Patna) became one of the most important political centres in ancient India, serving as the capital for major empires such as the Mauryas and the Guptas. However, it first rose to prominence during the earlier Magadhan kingdom. Knowing which ruler shifted the capital from Rajagriha (Rajgir) to Pataliputra helps you understand the early urban and strategic development of the Ganga valley.

Given Data / Assumptions:

• The region in focus is Magadha, an ancient kingdom in eastern India.
• The city in question is Pataliputra, which later became a famous imperial capital.
• The options list Ajatasatru, Kalasoka, Udayin and Kanishka.
• We assume basic knowledge that Rajagriha was the earlier capital of Magadha before Pataliputra rose to prominence.

Concept / Approach:
Historical tradition holds that King Udayin (Udayabhadra), the son and successor of Ajatasatru, was responsible for founding Pataliputra and shifting the capital there from Rajagriha. Ajatasatru did strengthen Magadha and may have begun fortifications at the confluence where Pataliputra later stood, but he is not typically credited with making it the official capital. Kalasoka (Kakavarna) came later, during the Shishunaga dynasty, and ruled when Pataliputra was already well established. Kanishka was a Kushan ruler from much farther northwest and is not associated with Magadha's capital at all. Therefore, Udayin is the correct answer.

Step-by-Step Solution:
Step 1: Recall that the earliest known capital of Magadha was Rajagriha (Rajgir). Step 2: Identify Ajatasatru as an important early king who expanded Magadha and fought neighbouring states. Step 3: Recognise that Udayin, Ajatasatru's successor, is credited with actually founding or fully developing Pataliputra and shifting the capital there. Step 4: Note that Kalasoka belonged to a later dynasty and ruled when Pataliputra was already functioning as a capital city. Step 5: Understand that Kanishka, a Kushan emperor, had no direct role in Magadha's capital shift. Step 6: Conclude that Udayin was the first to choose Pataliputra as the capital of Magadha.

Verification / Alternative check:
Standard Indian history textbooks and exam preparatory guides consistently attribute the foundation of Pataliputra as a capital to Udayin. They often describe a sequence in which Bimbisara and Ajatasatru ruled from Rajagriha, followed by Udayin's relocation of the capital to Pataliputra. Later dynasties such as the Nandas and Mauryas continued to use Pataliputra, cementing its importance. No mainstream source attributes the initial capital shift to Kalasoka or Kanishka, confirming Udayin as the correct answer.

Why Other Options Are Wrong:

• Ajatasatru: Important for military expansion, but the official shift of the capital to Pataliputra is attributed to his successor Udayin.
• Kalasoka: A later Shishunaga ruler who reigned when Pataliputra was already an established capital.
• Kanishka: A Kushan king who ruled in the northwest and had no connection with Magadha's capital shift.

Common Pitfalls:
Students sometimes choose Ajatasatru because his name is more familiar or because he is often credited with initiating defensive works near the Ganga. Another pitfall is general confusion among early Magadhan kings. To avoid errors, memorise the simple sequence: Rajagriha under Bimbisara and Ajatasatru, then Pataliputra as capital under Udayin, later used by Nandas and Mauryas.

Final Answer:
Pataliputra was first chosen as the capital of Magadha by Udayin.