Ahmad Shah Marashi was a Safavid Iranian Shah 1726 –1728 that succeeded Shah Tahmasp II, while the Shah was in the northern provinces fighting with Nader Shah Afshar

Nader Shah

Nāder Shāh Afshār ruled as Shah of Iran and was the founder of the Afsharid dynasty. Because of his military genius, some historians have described him as the Napoleon of Persia or the Second Alexander...

 against the Russians

Russians

The Russian people are an East Slavic ethnic group native to Russia, speaking the Russian language and primarily living in Russia and neighboring countries....

 and the Ottomans. Ahmad Shah Marashi was born as Mirza Seyed Ahmad Hossaini Marashi, eldest son of Mirza Abul Qasim Hossaini Marashi.

In the year of 1722, Mahmud Shah Ghilzai

Mir Mahmud Hotaki

Shah Mahmud Hotaki, , also known as Mahmud Ghilzai , was an Afghan ruler of the Hotaki dynasty who defeated and overthrew the Safavid dynasty to become the king of Persia from 1722 until his death in 1725.He was the eldest son of Mirwais Hotak, the chief of the Ghilzai-Pashtun tribe of Afghanistan,...

 invaded Iran and sacked the capital, Isfahan. By the year 1726, Mirza Seyed Ahmad seized the provinces of Fars and Kerman. In Kerman, the Marashi-Safavid noble, on behalf of Shah Tahmasp II, crowned himself Shah in the southern provinces on November 8, 1726. This was the perfect time, since the Afghan Ghilzai

Ghilzai

Ghilzai are the largest Pashtun tribal confederacy found in Afghanistan and Pakistan. They are also known historically as Ghilji, Khilji, Ghalji, Ghilzye, and possibly Gharzai...

Dynasty was having a political problem, thus leaving a vacuum to be filled up. But, Ashraf Shah Ghilzai invaded Kerman and defeated Ahmad Shah in 1728, thus ending his rulership. His execution took place on the banks of the Rud-e Zayande (Zayandeh River), near Oul-e Khwaju in August of 1728.

Source:

http://www.4dw.net/royalark/Persia/safawi5.htm Royal Ark