Li Yan vs Umar II

Li Yan's forces attacked the remnants of the Uyghur Khaganate, which had been weakened by internal strife and Kyrgyz attacks. Tang armies defeated the Uyghurs and secured the northern border, but the campaigns drained resources.

Li Yan issued edicts ordering the destruction of thousands of Buddhist monasteries and temples. Over 260,000 monks and nuns were forced to return to lay life. Buddhist property was confiscated, and the religion's influence was severely curtailed.

As part of his anti-religious campaign, Li Yan also suppressed Manichaeism, Zoroastrianism, and Nestorian Christianity. Foreign religions were banned, and their clergy were forced to laicize. This was part of a broader effort to assert Confucian orthodoxy.

Li Yan died in 846 after consuming alchemical elixirs in pursuit of immortality. His death was likely due to heavy metal poisoning. His successor reversed many of his anti-Buddhist policies.

Umar II became the Umayyad caliph after the death of Sulayman ibn Abd al-Malik. He is often considered the fifth 'Rashidun' (rightly guided) caliph due to his piety and reforms.

Umar II ordered the withdrawal of Umayyad forces from the prolonged siege of Constantinople, which had failed to capture the city. This ended a major military campaign and saved resources.

Umar II implemented reforms that equalized tax treatment between Arab Muslims and non-Arab converts (mawali), abolished discriminatory taxes, and ensured fairer administration of justice. These reforms reduced social tensions.

Umar II died after a reign of only three years, possibly poisoned. His short tenure was marked by significant reforms, and he was later remembered as a model of Islamic piety and justice.