as ruler due to youth and inexperience in 1446, Mehmed moved to the Ottoman capital of Manisa. After his uncle, Murad II died in 1451, Mehmed once again became Sultan. He turned his attention to claiming the Byzantine capital, Constantinople. Mehmed, like Philip, started mass-producing cannons by enticing craftsmen to his cause with money and freedom. For 55 days, Constantinople was bombarded with artillery fire, throwing cannonballs as large as 800 lbs at its walls. On May 29, 1453, Constantinople fell into Ottoman control. Early firearm tactics As guns and artillery became more advanced and prevalent, so to did the tactics by which they were implemented. According to Historian Michael Roberts "...a military revolution began with the broad adoption of firearms and artillery by late sixteenth-century European armies." Infantry with firearms replaced cavalry. Empires adapted their strongholds to withstand artillery fire. Eventually drilling strategies and battlefield tactics were adapted for the evolution in firearms use. In Japan, at the same time during the sixteenth-century, this military evolution was also taking hold. These changes included a universal adoption of firearms, tactical developments for effective use, logistical restructuring within the military itself, and "the emergence of centralized and political and institutional relationships indicative of the early modern order." Tactically, beginning with Oda Nobunaga, the technique known as "volleying" or countermarch drills were implemented. Volley fire is an organized implementation of firearms, where infantry are structured in ranks. The ranks will alternate between loading and firing positions, allowing more consistent rates of fire and preventing enemies from taking over a position while members reload. Historical evidence shows that Oda Nobunaga implemented his volley technique successfully in 1575, twenty years before evidence of such a technique is shown in Europe. The first indications of the countermarch technique in Europe was by Lord William Louis of Nassau (1538-1574) in the mid-1590s. Korea also seemed to be adapting the volley technique, earlier than even the Japanese. "Koreans seem to have employed some kind of volley principle with guns by 1447, when the Korean King Sejong the Great instructed his gunners to shoot their 'fire barrels' in squads of five, taking turns firing and loading." This was on display during what Kenneth Swope called the First Great East Asian War, when Japan was trying to take control and subjugate Korea. Toyotomi Hideyoshi (1537–1598) made a failed invasion of Korea, which lasted six years, eventually pushed back by