The need for defense and self-protection, which started in primitive ages, is still continuing today without losing any speed depending on technological developments and the type of threat. The defense industry, which has been targeted by enemy elements, especially military platforms, has been transformed into defense engineering in a wide range from personnel armor such as ballistic vest to developments in air platforms due to the developments in threats against personnel and headquarters. This study was conducted with a view to guide defense engineering and designs to be made on behalf of this engineering. Sometimes even an idea that seems small and useless can lead to concepts or industrial developments that have lasted for centuries. Considering the scientific studies in defense engineering, the factors affecting this engineering field were investigated. In summary, this book was written as a result of our harmonious work with a small group in mechanical engineering. The studies expressed in the scientific literature are sometimes blended with the contribution of our own studies. I would like to thank all my writers for their motivation in a short time. I would like to thank the academic staff of the Mechanical Engineering Department of the Turkish Military Academy (National Defense University) who contributed to the preparation of this book, and each of them for their valuable postgraduate students. There have been errors in the studies, deficiencies in the etiquette, and overlooked elements and even issues that we cannot address. We will look forward to positive and negative contributions in the next studies.