歐洲各國如何從中世紀的緩慢停滯、各自割據為陣的情勢，轉變成十五世紀起充斥戰爭與衝突的多國軍事競爭體系？本文嘗試從戰爭工藝（科技）、軍事組織、作戰方式、體系層級（包含國際與國家體系）四個層面進行探討。本文發現，在科技層面，十五世紀出現軍事科技上的重大突破，有效地將火藥應用到小型火器與大型火砲；在組織層面，國家逐漸捨棄雇用外國傭兵部隊的形式，轉變成建立自已的專業化軍隊；在作戰層面，受到新科技的影響，各國開始實驗新的作戰方式，使得攻城、守城、戰場對決都出現革命性的變化；在國際體系層級方面，外在文明的衰退與興起，同時給予歐洲機會與威脅，刺激歐洲軍事水準的提升；至於國家體系層級，歐洲各國之間的激烈競爭造成多國聯盟的組成與對抗，然而這些聯盟卻是極為多變與不穩定。如此歐洲從十五世紀起逐漸形成一個以軍事衝突為主軸的戰爭體系，為往後數百年的軍事競爭訂下基本格局。

How European countries transformed from a rigid feudal and isolated system into a multi-national system with fierce competition and frequent wars? This article tries to examine the issue from four dimensions: art of war, i.e., technology, military organization, tactics of warfare, and system-level conflicts (including two parts: Europe vs. outside civilizations, and wars among European countries). Our findings show that, first, there was a major breakthrough in firearm’s design and manufacturing technology by applying gunpowder to the small firearm and artillery; second, mercenary troops were gradually replaced by state-owned professional army; third, tactics of warfare have been revolutionized by experimenting various types of gunpowder firearms; and finally, European countries’ military strength has been stimulated and then upgraded by the outside threats such as the Ottoman empire, and the wars among European countries also created the possibility to form alliances based on common interests despite how unstable and short-life these alliances appeared to be. All these factors contribute to create a unique European war-system with extreme complexities and intensive competition for the next several hundred years to come.