Global security has faced more calamitous threats than it does in 2013, but seldom has it faced an array of challenges that pose such a complex challenge to defense planners.

As the map on the previous pages shows (expanded in its online version) the diversity of armed conflict is close to infinite. In the western Pacific, what China sees as its return to the world stage is causing tensions with its smaller and historically unfriendly neighbors and their ally, the United States, in a manner that reminds some of the 19th century rise of Germany. India and Pakistan are armed for, if not intent on, a combined-arms war that would be familiar from World War II.

Pakistan's nuclear weapons program and North Korean rocket technology have spilled over into Iran, which is driving towards becoming a nuclear power outside the web of treaties, protocols and inspections that have kept nuclear weapons from being used since 1945. Consequently Israel—target of Iran's rhetoric, proxy wars via Hezbollah and Hamas and nuclear missiles—is driven to a higher state of tension, not only attacking Hamas in Gaza, but apparently bombing a site in Sudan where rockets were being prepared for shipment to Gaza.

Sudan itself is part of an arc of instability across Africa that is destabilizing Mali at its western end, and, in the east, spills into the Indian Ocean as a continuing piracy threat. While militant Islamist leaders are involved in piracy, it is also about ransom and money for the desperately poor, from whom the world's pirates have always been drawn.

Indeed, war and criminal activity have not been so similar or so closely allied since the last of the old-world pirates were put down in the early 1800s. Drug cartels fight the government for effective control of Mexico, and support insurrections across South and Central America. What was once an exclusively military weapon, the submarine, has been re-created for bulk shipment of narcotics.

Distinguishing a military opponent from a criminal may be difficult in the Indian Ocean or the Gulf of Mexico. It is next to impossible in cyberspace, where the same piece of malware, the same source and the same methods may be used to exfiltrate data from a bank or a weapon design team, and where attacks on civilian infrastructure (such as power systems) can be used to hobble military deployments or equipment.

Cyberspace and near-Earth space, even more than the oceans, are part of the battlefield. Orbital space is another unique conflict environment, where there is a genuine fear that kinetic warfare could deny or compromise the use of space to victim, attacker and everyone else by unleashing a cloud of debris.

Other conflict environments differ widely from theater to theater. U.S. forces at any given time are deployed on or under water, in littorals, jungles and deserts and in 10,000-foot mountains, posing other problems.

The combat environment is just as diverse and complicated. The panoply of force protection—from body armor to protected vehicles and counter-rocket/artillery/mortar defenses—did not exist a decade ago. Strategist Andrew Krepinevich likes to talk about ”cost imposition strategies”: The use of improvised explosive devices is one such, employed very successfully against the developed world.

For military planners and their governments, there is another environment to be considered at all times—that of economics. In the U.S., the enormous cost of sustained boots-on-the-ground warfare, together with political unwillingness to raise taxes, has been a factor in driving national debt to crisis levels likely to force major changes in the armed forces and defense industry.

A cash-strapped United States is looking to allies to bear a higher share of what it sees as the common defense—the U.S spends 4.8% of its gross domestic product on its military while the best of its European allies struggle to make a 2% target. But those allies are trying to restrain their own domestic spending and their governments are under pressure to preserve social spending.

Demographic stresses complicate the economic trends. Aging populations require more maintenance, and there are relatively fewer young people, either to support them or join the armed forces. In the U.S., a decade of large-scale combat deployments has forced the services to pay more: Krepinevich calls the 50% increase in personnel costs “eating the budget from the inside out.”

The problem is to allocate resources to meet these many challenges. This involves accepting that there is not enough money to deal with them all as one would wish, and that means accepting risk in some areas. Picking those areas is what strategy is about.