How will human nature steer our nations over the coming decades? What are we evolved to do? The fundamental purpose of a living thing is to gather resources and reproduce. Some animals develop societies where the fundamental survival instinct of the individual is subsumed into the goal of protecting the social group. Human development of cities and defensive warfare addresses group survival under external threat. Our offensive warfare fundamentally addresses accumulation of resources required for survival. If you peel away all the layers of social rationalizations, at the base you will find this essential: human societies will react to future social threats attempting to insure survival of their nation states.
In his book The Rise and Fall of the Great Powers Paul Kennedy predicts that "no other state is likely to join the pentarchy of the United States, the USSR, China, Japan, and the EEC in the near future." When he wrote this in 1987, the triple threat of robotics, genetic engineering, and nanotech didn’t exist. Now, small nation states of limited wealth and resources can afford development of bioengineered genetic weapons. Statesmen worry about nuclear weapons in the hands of authoritarian regimes in Iran and North Korea. The advent of genetic engineering raises another destabilizing specter.
Nuclear weapons are very messy to use. They physically destroy their target’s resources and poison the surrounding area with radioactivity. This does not mesh well with the primary goal of offensive warfare, which is to accumulate resources. Genetically modified biological warfare agents, on the other hand, fit this goal perfectly. Done optimally, biological weapons destroy your enemy and leave his resources untouched. Bill Joy worries that artificial intelligence and nanobots are similar threats. While I don’t disagree, the barriers to entry are high for artificial intelligence and nanotech. Genetic engineered weaponized biological agents are here today. Laboratories working on biological weapons are easy to hide under the guise of medical research. They are even within the means of a sophisticated terrorist. The main practical issue is dispersal before the target mobilizes defenses. New developments in genetic engineering are already enabling new concepts in biologic weapon delivery. There will be a multitude of ways to stealthily infect your enemy target in the near future. Paul Kennedy’s pentarchy of International power will be replaced by "anarchic and competitive … rivalries between nations" ending the relative peaceful and prosperous history of the last century.
Not to single out small nations, another scenario would be a current religion wishing to selectively eliminate all unbelievers; thus keeping the world’s resources available for the chosen. It could be planned as a two stage attack. First the religion would fund a successful vaccine to a modern worldwide malady like the common cold or AIDS. Secretly they would attach a non-functional component that would cause rapid death if turned on by a unique amino acid trigger. To demonstrate the religion’s humanitarianism they would offer a free version of the vaccine and invent a religious reason why all believers had to use a more expensive (acceptable to their God) version. After a few years everyone in the world would be vaccinated. Then the second stage; the ‘missing key’ trigger amino acid which causes death would be attached to a mild but hyper-virulent version of the flu. This flu would be simultaneously released worldwide. By the time that the world recognized that practitioners of the religion were immune most of the unbelievers would be dead.
Another scenario is described in the Tom Clancy novel, Rainbow Six, which involves a plot to unleash an engineered virus on humanity by infecting Olympic Games attendees with a virus carefully engineered to maximize virulence and lethality to the human host after enough time to infect others, in order to wipe out humanity except for the chosen few who had been immunized.
Large nations have the most resources available and would not likely be able to wait years or keep such biological weapons secret. Here a more likely scenario is dispersal of weaponized plague or flesh eating bacteria by a multitude of dispersal agents including animal vectors, autonomous aerial release, and water supply injection.
If these scenarios seem farfetched; consider that the Holocaust was only 55 years ago. A number of current societies are similarly xenophobic. There are both Muslim and Western groups that deny the Holocaust occurred, calling it a Jewish conspiracy. If Hitler could have infected kosher food with a delayed release non-infectious virus he would have used it. If historical revisionists can successfully guide their adherents to believe a re-write of one of the most despicable periods in modern history... what else can they rationalize? After World War Two, Eric Hoffer wrote in his preface to THE TRUE BELIEVER Thoughts on the Nature of Mass Movements,
"All mass movements generate in their adherents a readiness to die and a proclivity for united action; all of them, irrespective of the doctrine they preach and the program they project, breed fanaticism, enthusiasm, fervent hope, hatred and intolerance; all of them are capable of releasing a powerful flow of activity in certain departments of life; all of them demand blind faith and single hearted allegiance."
Mass movements arise not among the impoverished, but instead among relatively well-off middle classes facing loss of what they view as their entitlements. It is this middle class group that most easily yields their allegiance to a fanatic.