Upon the death of Emperor Libne Dengil in 1540, his son Gelawdiwos was proclaimed Emperor and King of Kings. He was given the royal nom-du-guerre of Atsnaf Seged, which translates to "He to whom the horizon bows" in Ge'ez. Gelawdiwos was still a young man, yet he had proven himself repeatedly on the field of battle against the Islamic forces of Gragn Mohammed (Ahmed Ibn al Ghazi). As he was still very young though, his mother Empress Seble Wongel assisted him in the earlier part of his reign, although not actually given the formal title of regent. Empress Seble Wongel was from northern Tigrai on one side of her family, and from Simien on the other side. Both these areas had often been a source of troublesome and persistent rebellion against previous monarchs. Now however, these districts became fiercely loyal to the new Emperor because of this blood tie. The beginning of his reign was marked with some significant successes against the forces of the now dominant Gragn in Tembien and Shirre districts which were controlled by Yonathan, son of Henok who had defected from Emperor Libne Dengil to Gragn. The Emperor crushed the Moslem forces and killed Yonathan. While recovering from these battles in Simien, a force of 600 well armed Portuguese soldiers arrived from India and landed at Massawa. They defeated the Turkish governor of Massawa, Noor id Din, and after his death in battle, they cut off his head and sent it to the Empress Seble Wongel. They joined their forces with the army of the Bahir Negash Yeshaq, and marched to the monastery of Debre Damo to meet with Empress Seble Wongel who was encamped with her own army nearby. The widowed Empress, the Bahir Negash and the Portuguese prepared for battle against the Moslems. Gragn became quite alarmed at the possiblity that the young Emperor Gelawdewos would combine his forces with is mother and the Portuguese, so he decided to act swiftly and marched into Akale Guzai (in modern day Eritrea). There in March of 1541, at the battle of Anasa he fought the combined forces of Empress Eleni and the Portuguese under Christoforo Da Gama. For the first time the Harrari and Adal forces were faced with Canons, things they had never seen before. Gragn was wounded and fled the scene of battle. He immediately sent a plea to the Pasha of Yemen for more arms. Zebied Pasha sent a force of 2000 Arabs and Turks to back up Gragn's forces. In August of 1541, the Empress and the Portugese again met and fought Gragn at Ashenge. The commander of the Portugese, Dom Christoforo Da Gama was severly wounded. In the haste of retreat, Da Gama was hidden in a forest so that his wounds could heal before making his way to rejoin the army. While hidden in this wood, a young Turkish girl whom Da Gama had kept as his mistress apparently decided to betray him, and led the Muslims to where he was hidden. His captors beat him severely and dragged him before Gragn. They tried to get him to reveal where the Empress and the Portugese had retreated to but he refused. Gragn then approached the prisoner, and told him that if he were to accept Islam, he would be merciful to him. Da Gama is said to have spat in Gragn's face, where upon he was again severely beaten. Gragn then grabbed an axe and personally beheaded the son of Vasco Da Gama.

In the mean time, Emperor Gelawdewos had finally arrived from Simien with his army, and joined them with the forces of his mother and the Portugese. The appearance of the young Emperor apparently greatly cheered the Ethiopian and Portugese soldiers and they rallied behind him with great enthusiasm. The news of the Emperor's arrival and the rallying of his fresh forces in combination with the veterans of the Empresses army and the Portugese sent a tremor of hope through the Christian population. Soon thousands began to flock to his banner from Shewa and Tigrai, from Amhara Sayint, Wag, Lasta and the rest of Wollo, from Gojjam and Beghemidir, from Hamasein and Tigre. The Emperor then marched to Wegera and clashed with Gragn's forces. It was to be a great victory for Gelawdiwos, and several of Gragn's greatest generals were killed. Many others surrendered and groveled before the Emperor carrying rocks of repentance on their shoulders, begging for his mercy. The Emperor ordered the large house and Mosque that Gragn had built at Wegera be destroyed without a trace. Gragn himself gathered up his forces and marched on the Emperor. The two forces met at Fogera on the Banks of Lake Tana, in February of 1542, and engaged in a huge and bloody battle. During the battle, a loyal Portugese servant of Dom Christophoro named Pedro Leon saw the opportunity to avenge his master and shot Gragn wounding him severely. Gragn, so as not to panic his troops is said to have simply stated "Fight on" and went to sit under the cover of a boulder so as not to show how seriously he was hurt. Leon however had seen him, and he followed him there and finished him. He cut off Gragn's ear and displayed it to the jubilant Portugese and Ethiopians who swirled around him in victory. However, just before the battle, the Emperor had promised his sister's hand in marriage "..to he who brings me the head of Gragn." So an Ethiopian soldier quickly went to the corpse and severed the head and presented it to the Emperor, claiming the Princess. The Emperor had already been presented with Gragn's ear by Leon, and so he refused to give his sister to the soldier on the grounds that he did not actually kill Gragn. He gave him a large reward in gold instead. The site of Gragn's death is known as Gragn Ber (Gragn's gate) to this day. Thus ended the remarkable life of Imam Ahmed Ibn Ibrahim Al Ghazi, known to his enemies as Mohammed Gragn.