The Germiyan attempted to declare independence from the
Seljuk Sultanate of Rum when
Mesud II became the
sultan following the execution of his father,
Kaykhusraw III, by the Mongols in 1283. The conflict between the Germiyanids and the
Seljuks went dormant upon Mesud II's death, and Yakub agreed to become a vassal of the new ruler,
Kayqubad III. At that time, Yakub's realm extended as east as
Ankara. His domain included
Denizli and
Karahisar in western
Anatolia, according to
Nicephorus Gregoras, and
Tripolis on the Meander, according to
George Pachymeres. Contemporary historian
al-Umari described Yakub as the most powerful Turkish
emir, being the suzerain of many of his neighbors, with the
Byzantine Empire paying him 100,000 pieces of gold each year. Al-Umari further relayed the observations of travelers Haydar al-Uryan and Balaban, that Yakub's domains included about 700 settlements. He possessed 40,000 cavalry and was able to raise 200,000 troops in times of war, although historian Varlık considers this number exaggerated. Yakub eventually conquered the regions of
Simav and
Kula, which were later regained by the
Catalan Company. Similarly,
Philadelphia (later known as Alaşehir), which he had earlier taken over, was lost to the Catalans in the spring of 1304, but the town started paying him
jizya by 1314. Yakub had hostile relations with the
Ottoman Beylik, and provoked the
Tatars of the
Chavdar tribe near
Karacahisar to attack them in 1313. After having eliminated the
Hamidid and
Eshrefid begs in 1325,
Timurtash, the
Ilkhanid governor of Anatolia, attempted to enact authority over the rulers of western Anatolia and seize the territory of Germiyan, Philadephila, Denizli, and Menteshe. Yakub's son-in-law, who was the lord of
Afyonkarahisar, fled to
Kütahya from
Eretna, who was an officer under Timurtash tasked to capture the city. When Yakub was about to engage in a battle with Eretna, the latter was called back by Timurtash in 1327. The region under Yakub was economically prosperous and saw an increase in literary and scientific patronage.
Rumi's grandson
Ulu Arif Chelebi visited the region by 1312 and maintained spiritual authority over Yakub. Yakub struck a single type of coin late into his reign. An unnamed coin minted in 1307 mentioning the title
Khan-i Germiyan is identified with Yakub I. In the inscriptions of the castle of
Sandıklı, which were later moved to a nearby fountain, he was referred to as
Sultan al-Germiyaniyya Chelebi al-Azam azzamallahu kadrehu. Yakub owned a
waqf (charitable endowment) for the
mevlevihane (congregational place for the
Mevlevi Order) of Karahisar. According to
İsmail Hakkı Uzunçarşılı, he possibly owned another
waqf at the
zawiya of the village of Hacim near
Uşak, which dates to 1321. However, there the owner's father was recorded as Mehmed. Yakub is known to have exchanged letters with the
Mamluk Sultanate in 1340; these are the latest known records of his life, and his exact year of death is unknown. According to the 17th-century traveler
Evliya Çelebi, who wrote three centuries after Yakub's death, he was buried at the hill of Hıdırlık near Kütahya.
Mehmed, nicknamed
Chakhshadan, was the son and successor of Yakub. ==Family==