Throughout history the primary form of deterrence has been defences. These have been both passive and active. Passive defences include fortifications, moats and natural features such as rivers, oceans and high ground, and serve to deter by making attacks more difficult and costly. Active defences and their ability to deter can best be summed up by the quotation frequently attributed to President Theodore Roosevelt: "Speak softly and carry a big stick." Effectively, this involves military defence forces.

However, military capability and fortifications are not the only way, nor arguably the best way, to deter. Economic self-interest may deter. Just as an employee is restrained from insulting his employer or a businessman from annoying his customer, nations may be restrained from some adventures either by the direct cost or by the harm to future trade and other economic activity that may result. Building economic interdependency can therefore be considered as a form of deterrence.