The victorious Mercha Kassai was subsequently declared Yohannes IV on 21 January 1872. In 1875 and 1876, Turkish/Egyptian forces, accompanied by many European and American 'advisors', twice invaded Abyssinia but were initially defeated: once at the Battle of Gundet losing 800 men, and then in the second invasion, decisively defeated by Emperor Yohannes IV at the Battle of Gura on 7March 1875, where the invading forces lost at least 3000 men by death or capture. At the council of Boru Meda in 1878, Yohannes came out with a decree that Ethiopian Muslims must accept Christianity or be banned. Those that refused were executed on the spot. Tens of thousands were killed and more left their land and belongings to flee to Harar, Bale, Arsi, Jima and even to Sudan. From 1885 to 1889, Ethiopia joined the Mahdist War allied to Britain, Turkey, and Egypt against the Sudanese Mahdist State. In 1887 Menelik king of Shewa invaded the Emirate of Harar after his victory at the Battle of Chelenqo. On 10 March 1889, Yohannes IV was killed by the Sudanese Khalifah Abdullah's army whilst leading his army in the Battle of Gallabat (also called Battle of Metemma).