Early modern warfare is the era of warfare following medieval warfare. It is associated with the start of the widespread use of gunpowder and the development of suitable weapons to use the explosive, including artillery and firearms; for this reason the era is also referred to as the age of gunpowder warfare (a concept introduced by Michael Roberts in the 1950s). This entire period is contained within the Age of Sail, which characteristic dominated the era's naval tactics, including the use of gunpowder in naval artillery. All of the Great Powers of Europe and the Islamic gunpowder empires were actively fighting numerous wars throughout this period, grouped in rough geographical and chronological terms as: The European wars of religion between the 1520s and the 1640s (including the Thirty Years' War, the Eighty Years' War and the Wars of the Three Kingdoms) and, the Franco-Spanish War (1635–1659), the Northern Wars, Polish–Swedish wars and Russo-Swedish Wars; The Russo-Turkish Wars, Ottoman–Habsburg wars, and other Ottoman wars in Europe. In the Horn of Africa, the Adal's conquest of Ethiopia and the involving of the Ottomans, Mamluks and the Portuguese. In Asia, the Persia–Portugal war, Nader's Campaigns, the Mughal conquests, the Anglo-Mysore Wars, the Japanese invasions of Korea (1592–1598), and China's Transition from Ming to Qing followed by the Ten Great Campaigns Throughout the 18th century the "Second Hundred Years' War", an umbrella term which includes the Nine Years' War, Seven Years' War, War of the Spanish Succession, War of the Austrian Succession, American War of Independence (American Revolutionary War), French Revolutionary Wars and the Napoleonic Wars of the late 18th to early 19th centuries which mark the end of this era. Europe Beginning of polygonal fortifications The period from 1501 to 1800 saw a rapid advance in techniques of fortification in Europe. Whereas medieval castles had relied on high walls to keep out attackers, early modern fortifications had to withstand artillery bombardments. To do this, engineers developed a style of fortress known as the "Italian style" or trace Italienne. These had low, thick, sloping walls, that would either absorb or deflect cannon fire. In addition, they were shaped like stars, with bastions protruding at sharp angles. This was to ensure that every bastion could be supported with fire from an adjacent bastion, leaving no dead ground for an attacker to take cover in. These new fortifications quickly negated the advantages cannon had offered to