Osman I (1258-1326), the foreign language name Osman I, was the founding sultan of the Ottoman dynasty in Türkiye. Born in Seyute, northern Türkiye, he was the son of Eltulururgazi, the tribal leader. When he was young, he led the tribe to guard the border of the Roma dynasty. Later, he took advantage of the decline of the Roma dynasty and started his own army to stand on his own feet. In 1299, he ascended the throne and called Ghazi, using his name Osman as the national title. During his reign, he worked hard to lay the foundation for the Ottoman dynasty to become a powerful empire across Asia, Europe and Africa. He died of illness in 1326, aged 68, and reigned for 27 years.

In his early years, Ottoman practiced martial arts with his father and assisted him in guarding the borders of the Sultanate of Rum. He studied Sufi philosophy at the local Sufi elder Edbaliyo and married his daughter Malhadon.
In 1281, he succeeded his father as the tribal leader and took over the position of Bayi at the border. He formed an alliance with the leader of the Sophie Order and the Gazi Society (an organization of free people), gradually increasing his political prestige. He recruited troops, strengthened military strength, and continuously expanded outward. He led his army to defeat Byzantine mercenaries multiple times and successively occupied fortresses such as Karajahisar, Bilejik, and Yarhisar, with the capital located in Yenissehir.
In 1289, the Sultan of Rum was forced to recognize all the territories he had seized as his fiefdom. At the end of the 13th century, the royal family of the Rum Sultan declined, and the small Turkic principalities within their borders became independent.
In 1299, the Ottomans took advantage of this opportunity to officially declare independence, known as "Gazi", and established the Ottoman dynasty, becoming one of the powerful duchies in Asia Minor. When he was in power, he declared Sunni doctrine as orthodox faith and followed the teachings of the Hanafi school. Domestic religious issues were decided through consultation among jurists. Ottoman himself had a devout faith, adhered to religious practices, lived frugally, and had a strong spirit of holy war. He once paid tribute to the Ilkhanate of Persia on behalf of the principalities of Türkiye Minor Asia. According to historical records, after Ottoman's death, his family only had dozens of weapons, over 10 horses, and over 200 sheep. Türkiye's historical records call it "tribal leader, Ghazi hero".
The Ottoman Empire may have been the most famous emperor in history, with its name becoming the name of the Ottoman Empire for over 600 years. This vast empire spans across three continents of Asia, Africa, and Europe, choking the throat of mainland transportation. It has long been one of the strongest and most prosperous empires in the world.

Turks, a nation that has experienced many vicissitudes in the great migration of nations in the world, have left their footprints from the western Iranian plateau to Asia Minor. In Asia Minor, they became the people of Allah. Later, under the pressure of the Mongols, about 400 of their households were under the leadership of Ertu Grul ğ Under the leadership of Rul, he moved to Asia Minor and found a place to settle down on this beautiful land. At that time, most of Asia Minor was controlled by the Roma Sultanate of Turks. The Roma Sultanate gave generous treatment to fellow Ottomans and granted the Suogud region in northwest Asia Minor bordering the Byzantine Empire to Ertugrur as a vassal to defend the Roma Sultanate. Eltugrul was Ottoman's father.
In 1290, Ertulururgazi died, and at the age of 32, Ottoman succeeded as the leader. At that time, the international situation had undergone significant changes. While the Ottoman state was thriving, its suzerain, the Sultanate of Rum, fell apart under repeated attacks from the Mongols. In 1308, it finally came to an end. At the critical moment, Osman took over the banner of Türkiye and declared independence in 1299, calling himself Emir.
In 1300, he called himself Sudan (meaning the most authoritative person), which was the source of the Ottoman Türkiye Empire for more than 600 years.

Ottoman was an outstanding military strategist and organizer, under his leadership, the Ottoman country continued to grow and develop. In addition to his outstanding personal talent, there are also several reasons for his success:
1. He raised the banner of holy war and, in the name of God, united religious and semi religious groups under his banner, gathering them into a powerful force;
2. He generously bestowed land upon those who had made contributions in the holy war, thus winning the hearts of the people;
3. He has a broad mind. In addition to Turks, he has also accepted a large number of Muslim fighters from other ethnic groups, even non Muslims.
Lucky marriage enhances prestige
Ottoman was appreciated by the respected Sufi elder Sheikh for his talent and magnanimity, and married Sheikh's daughter Mal'ha. This fortunate marriage greatly helped the Ottoman hegemony, as Sheikh's reputation led to more Muslim soldiers defecting to the Ottoman flag. When Sheikh ascended to the Ottoman throne, he presented him with the sword "Sword of Victory", which later became a sacred item bestowed upon successive Ottoman monarchs.
Expanding to the Byzantine Empire
Ottoman always avoided attacking his former suzerain, the Sultanate of Rum. After the downfall of the Sultanate of Rum, due to its insufficient national strength and strategy, he also recognized the Ilkhanate that ruled Persia as the suzerain, representing the various principalities of Asia Minor to pay tribute to the Mongolian court. The main goal of Ottoman expansion was the pagan Byzantine Empire. Byzantium, a millennium old country, was now like an old man suffering from a chronic illness. Its army was mainly mercenaries, and there was no longer any support from the Crusaders of the Eastern Expedition. Under the attack of the Ottomans who united under the name of Allah, it gradually retreated.

Towards the Dream of Europe
The Byzantine cities occupied by the Ottomans included Eskishir, Lefkai, Kagahisar, Inegre, and Yenishir. He won the title of "Bey" for defeating the Byzantine army in the Battle of Bafaeron in 1301. After occupying the city of Melano in northwest Asia Minor, he renamed it Kagahisar and relocated its capital here as a stronghold for further advancement.
Next, the Ottomans targeted the last stronghold of the Byzantine Empire in Asia Minor - Bursa. Once Bursa was captured, the Strait of Marmara leading to Europe was revealed before their eyes. This siege was very difficult and lasted for 9 years. As the city was about to break, Ottoman's life also came to an end.

In 1326, Ottoman passed away after leaving a will for his son Orhan, stating "to be fair, kind, to cherish scholars, and to protect the people.". Orhan captured Bursa and moved the capital here, burying the Ottoman body in this city, making Bursa a a holy city for the Ottomans. During the reign of Orhan, the Ottoman state continued to develop and grow. The Ottoman Empire, from its founder Ottoman to the 10th Sultan Sultan Suleiman the Great, maintained an upward trend for over 300 years (although it had been defeated by Timur, its strength remained unchanged). Its successors, including Olhan, Murad I, Mohammed II, Selim I, and Suleiman I, were all outstanding commanders that never existed, making the empire's territory expand like a balloon, until it destroyed the ancient Byzantium and dominated the three continents.

In 1299, Ottoman I declared his country an independent duchy.
In 1301, they attacked the already declining Byzantine Empire and occupied most of Byzantine Anatolia, where Byzantine rule was on the verge of collapse. It encroached on Byzantine fortresses like Ephesus in Asia Minor.
And in 1317, they attacked the heavily guarded city of Bursa near the Byzantine capital Constantinople, but the Byzantine army persisted in resistance. Until eventually losing its ability to resist, Byzantium abandoned resistance and declared surrender in 1326 (the 10th year of the siege of Bursa). But Ottoman I was seriously ill. He passed away shortly before moving the capital to Bursa. After his descendants moved the capital to Bursa, they buried Ottoman I in a mosque in Bursa. The successor, Orhan, continued to attack the Byzantine Empire and expand outward. Quickly occupied all areas of Nicaea and Byzantium in Asia Minor.
During the Ottoman rule, the Turks gradually moved from nomadism to settled life.

From a historical perspective, during the Ottoman era, his country was still a small country on the Anatolian Peninsula and had just entered a stable state stage. The world empire spanning three continents is the result of the continuous efforts of its successors. But this cannot deny the influence of Ottoman, without Ottoman as the pioneer, there would be no such thing as later. The rise of the Ottoman Empire has given the Islamic world, which has been torn apart since the collapse of the Arab Empire, a backbone. Moreover, because Türkiye has blocked the land route of east-west traffic, Western Europeans have to look for new traffic lines from the sea, so there is a later era of great navigation.