Sonam Rapten, also Sonam Choephel was regent

Regent

A regent, from the Latin regens "one who reigns", is a person selected to act as head of state because the ruler is a minor, not present, or debilitated. Currently there are only two ruling Regencies in the world, sovereign Liechtenstein and the Malaysian constitutive state of Terengganu...

 in Tibet

Tibet

Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...

 from 1642 tot 1658. Soon after his nomination as a regent, he was appointed Ganden Podrang as well.

According to the 14th Dalai Lama

14th Dalai Lama

The 14th Dalai Lama is the 14th and current Dalai Lama. Dalai Lamas are the most influential figures in the Gelugpa lineage of Tibetan Buddhism, although the 14th has consolidated control over the other lineages in recent years...

 he was the chief attendant of the 4th Dalai Lama, who discovered the incarnation of the 5th Dalai Lama.

During the youth of the 5th Dalai Lama, Rapten requested the aid of Gushi Khan

Güshi Khan

Güshi Khan , a Khoshut prince and leader of the Khoshut Khanate, who had supplanted the Tumed descendants of Altan Khan. His military assistance to the Gelug school enabled the 5th Dalai Lama to establish political control over Tibet...

, a powerful Mongol military leader, in order to end the Gelug

Gelug

The Gelug or Gelug-pa , also known as the Yellow Hat sect, is a school of Buddhism founded by Je Tsongkhapa , a philosopher and Tibetan religious leader...

prosecution and establish this order as the lead order of Tibet.