Explanation:

The most important political developments of the Post-Maurya period was the onslaught of for-eigners from the north-west.
The first among them were the Bactrian Greeks, known in earlier Indian literature as Yavanas; the word was derived from the Old Persian from Yauna, signifying originally Ionian Greeks but later all people of Greek nationality.
The first to invade India were the Greeks or Bactrian Greeks who were called the Indo-Greeks or Bactrian Greeks in the early second century B.C. The history of the Indo-Greeks has been recon-structed mainly on the evidence of their coins bearing legends in Greek and later in Brahmi as well.
Demetrius, son of Euthydemus, king of Bactria was perhaps the first foreign (Indo-Greek) king after Alexander who carried Greek arms into the interior of India. He reduced to submission a considerable portion of Afghanistan, the Punjab and Sind.
The best remembered of the Indo-Greek kings was Menander, (165-145 D C.) who, as Milinda, attained fame in the Buddhist text Milindapanho or the question of Milinda-a catechismal discussion in Buddhism supposedly conducted by Menander and the Buddhist philosopher Nagasena, resulting in Menander’s conversion to Buddhism.
Menander stabilised Indo-Greek power, in addition to extending its frontiers in India.
He had his capital at Sakala (modern Sialkot) in Punjab. There is little doubt that the attempted to conquer territory in the Ganges valley, but he failed to retain it. He may well have attacked the Sungas in the Yamuna region, if not Pataliputra itself. A Brahmi inscription engraved on a Garuda Pillar found are Besnager near Bhilsa records that Antialkidas of Taxila sent an ambassador, named Heliodorus, to the court of Kasiputra Bhagabhadra, identified with the last but one Sunga, Bhagavata.