Western countries are running out of people to fight their wars. This is even more acute given the traditional and current demographic trends in both armed forces and general populations.
A shift to cyber conflict can help the West maintain parity over Eastern methods of assymetrical warfare (by human attrition /cyber conflict).
Declining resources will lead to converging conflicts of interest and dynamics in balance of power in the 21 st century.
The launch of Sputnik by USSR led to the moon shot rush by the US.1960s
The proposed announcement of StarWars by USA led to unsustainable defence expenditure by USSR.1980s
The threat of cyber conflict and espionage by China (and Russian cyber actions in war with Georgia) has led to increasing budgets for cyber conflict research and defense in USA. -2010s
If we do not learn from history, we are condemned to repeat it.
Declining Populations in the West and Rising Populations in the East in the 21 st century. The difference in military age personnel would be even more severe, due to more rapid aging in the west.
Economic output will be proportional to number of people employed as economies reach similar stages of maturity (Factor-Manufacturing-Services-Innovation)