During his reign as governor of Trabzon Selim had earned a great reputation among his military men for his confrontations with the Safavids, slave raids and a campaign in the Caucasus against Georgia.

[9] In 1505 Selim routed a 3,000-strong Safavid army led by Shah Ismail's brother, massacring many and seizing their arms and munitions.

[10] In 1507, after Shah Ismail marched through Ottoman lands to wage war against the Dulkadirids, Selim attacked Erzincan and defeated another Safavid army sent against him.

[11] The following year he invaded the Caucasus, subdued western Georgia, brought the Imereti and Guria under Ottoman domination and seized a large number of slaves.

[citation needed] One of Selim's first challenges as sultan involved the growing tension between the Ottoman Empire and the Safavid Empire led by Shah Ismail, who had recently brought the Safavids to power and had switched the Persian state religion from Sunni Islam to adherence to the Twelver branch of Shia Islam.

By 1510 Ismail had conquered the whole of Iran and Azerbaijan,[17] southern Dagestan (with its important city of Derbent), Mesopotamia, Armenia, Khorasan, Eastern Anatolia, and had made the Georgian kingdoms of Kartli and Kakheti his vassals.

Early in his reign, Selim created a list of all Shiites ages 7 to 70 in a number of central Anatolian cities including Tokat, Sivas and Amasya.

The Battle of Chaldiran was of historical significance: the reluctance of Shah Ismail to accept the advantages of modern firearms and the importance of artillery proved decisive.

This led to the Ottoman annexation of the entire sultanate, from Syria and Palestine in Sham, to Hejaz and Tihamah in the Arabian Peninsula, and ultimately Egypt itself.

This permitted Selim to extend Ottoman power to the Muslim holy cities of Mecca and Medina, hitherto under Egyptian rule.

In fact, Selim did not make any claim to exercise the sacred authority of the office of caliph, and the notion of an official transfer was a later invention.

[27] A planned campaign westward was cut short when Selim was overwhelmed by sickness and subsequently died in the ninth year of his reign aged 49.

A famous anecdote relates how another vizier playfully asked the Sultan for some preliminary notice of his doom so that he might have time to put his affairs in order.

[37] Paolo Giovio, in a work written for Charles V, says that Selim holds Alexander the Great and Julius Caesar in the highest esteem above all the generals of old.

The sultan hoped to lure Ismail into an open battle before his troops starved to death, and began writing insulting letters to the Shah, accusing him of cowardice: They, who by perjuries seize scepters ought not to skulk from danger, but their breast ought, like the shield, to be held out to encounter peril; they ought, like the helm, to affront the foeman's blow.Ismail responded to Selim's third message, quoted above, by having an envoy deliver a letter accompanied by a box of opium.

Opposed to Shah Ismail's adherence to the Shia sect of Islam (contrasting his Sunni beliefs), Selim I and his father before him "did not really accept his basic political and religious legitimacy,"[40] beginning the portrayal of the Safavids in Ottoman chronicles as kuffar.

[41] After the Battle of Chaldiran, Selim I's minimal tolerance for Shah Ismail disintegrated, and he began a short era of closed borders with the Safavid Empire.

[44] So strict was this embargo that, "merchants who had been incautious enough not to immediately leave Ottoman territory when war was declared had their goods taken away and were imprisoned,"[44] and to emphasize frontier security, sancaks along the border between the two empires were given exclusively to Sunnis and those who did not have any relationship with the Safavid-sympathizing Kızılbaş.