Concepts and theories of warfare have changed radically over the past 20 years, leading to changes in armies' fighting doctrines in numerous countries across the world. Non-conventional security threats that have emerged in the global arena during the last two decades have led to the birth of new military concepts; asymmetric warfare has become a reality for numerous armed forces in various regions, while electronic/cyber warfare is no longer confined to the realm of theory.

The opening years of the 21st century have brought with them new security regimes in various regions. This has encouraged countries to reshape their perceptions and expectations for the future, and adapting to these changes has become one of the most difficult challenges facing strategic planners.

The 9/11 attacks contributed significantly to shaping the features of a new world in which strategic thinking is quite different, invalidating previous concepts and expectations regarding the future of warfare and re-writing both military doctrine and theory. The most pressing questions for strategists no longer concern the volume of a nation's defense spending or its ability to face conventional threats. Rather, the primary concern is how best to direct and distribute financial appropriations to keep pace with these new threats.