Janissary Corps in the context of Ottoman sultan

The Auspicious Incident or Auspicious Event (Ottoman Turkish: وقعۀ خيريّه, romanized: Vak'a-i Hayriyye, lit. 'The Fortunate Event' in Constantinople; Vaka-i Şerriyye, "Event of Malignity" in the Balkans) was the forced disbandment of the centuries-old Janissary Corps by Ottoman Sultan Mahmud II on 15 June 1826. Most of the 135,000 Janissaries revolted against Mahmud II, and after the rebellion was suppressed, most of them were executed (6,000 or more), exiled or imprisoned. The disbanded Janissary corps was replaced with a more modern military force.

The Ottoman Army was the military of the Ottoman Empire after the country was reorganized along modern western European lines during the Tanzimat modernization period. In 1826, Sultan Mahmud II abolished the Janissary Corps, which had existed for centuries but was unable to adapt to modern military tactics and frequently rebelled. In its place, he established the Asakir-i Mansure-i Muhammediye (Victorious Soldiers of Prophet Muhammad) army that same year. The Sultan continued his reform efforts by establishing modern institutions to support the army. In 1826, he established the Seraskerlik , equivalent to a modern Ministry of Defense. In 1827, the first military medical school,Imperial School of Medicine, was opened to train doctors and surgeons for the army. In 1834, Harbiye Military School was opened with the support of French military instructors to train officers for the army.

On June 14, 1843, Sultan Abdülmecid changed the army's name to Asâkir-i Nizâmiye-i Şâhâne (Royal Regular Soldiers). From this date onward, the army began to be known simply as the Nizami Ordu (Regular Army). In 1845, he established Kuleli Military High School, the first modern military high school, in the capital Istanbul. In 1848, the first military academy, Erkan-ı Harbiye Military Academy, was opened to train army staff officers and high-ranking officers, or pashas. The Crimean War was the first war effort in which the modern army took part in, proving itself as a decent force. The last reorganization occurred during the Second Constitutional Era.

The Russo-Turkish War of 1828–1829 resulted from the Greek War of Independence of 1821–1829; war broke out after the Ottoman Sultan Mahmud II closed the Dardanelles to Russian ships and in November 1827 revoked the 1826 Akkerman Conventionin retaliation for the participation of the Imperial Russian Navy in the Battle of Navarino of October 1827.

The Ottoman Empire had bloodily abolished its centuries-old regular army, the Janissary Corps, in 1826. A year later, Great Britain, France, and Russia jointly raided the Ottoman Navy at Navarino. When war broke out between the Ottomans and Russia in 1828, the Ottomans possessed neither a regular army nor a navy. After suffering several defeats, both in the Balkans and in the Caucasus, the Sultan decided to sue for peace, which resulted in the signing of the Treaty of Adrianople on 14 September 1829.