It was not surprising that the mass-media response to the 2015 U.S. defense budget was that it would result in “the smallest Army since before World War II.” It would have been a shock had anyone continued: “and it's a good thing.” But it is—and Russia's current actions in the Crimea do not change that fact.

Reversing the early-2000s growth in land forces is a start on what has to be a “four-FYDP” (future years defense program) effort—20 years—to forge a future-relevant military.

Today's force has its roots in an era when wars were fought on the land and on the sea, zealots explored the air, scientists dreamed of space, and cyber did not exist. Forces had to be within visual range in order to gauge each other's strength and start thinking about tactics. The intelligence, surveillance and reconnaissance (ISR) role was in the embryo stage.

But even in 1939, the boot-centric view of warfare was on shaky ground. Large standing armies with professional leadership were an idea less than 100 years old. The Greek and German classic studies of warfare were based on Europe—then as now unique in short distances and high population density.

Historians bemoan the pre-WWII U.S. Army's lack of readiness and its reversion to pre-1917 habits. But a nation that had no fear of land invasion did not need to make its Army a priority. That is the case today.

The argument that land forces have special strategic significance is weak. The record of boots-on-the-ground wars is that they usually cause more problems than they solve (AW&ST April 1/8, 2013, p. 12). The argument that they are the U.S.'s prime military means, or that other services exist only to support them and get them to the fight, is neither realistic nor helpful.

Globally, there are few cross-border land threats to which the U.S. would respond. North Korea's shift of resources to missile technology means land attack is no longer the main threat to the South. It takes a stubborn refusal to read headlines or history to think the U.S. will send land forces across borders to promote democracy again, at least for a long time.

Events in Ukraine and the Crimea—combining ethnic, civil and international strife—provide a case in point. The strongest conceivable U.S. land or amphibious forces would not provide a military option. In the long term, the most significant effect of the Russian action may be to convince the Putin regime to pursue a military that it can't afford, a policy that did not exactly work out well for the Soviet Union.

Absent major land wars, future conflicts will either be centered on ethnic issues—not along national boundaries, but within or across them—or will involve threats to the global commons, whether at sea, in the air, in space or in the domain of communications.

The air and the sea will be the most important domains for U.S. military power in the next decades, with space and cyber assuming growing importance, and ISR, mostly from the air and space, as the connective tissue for every military action.

Trade and prosperity make the commons important. We will have to recognize a marked change in the motivation of future strategy, in that it will be based on national, material self-interest. There is nothing wrong with such a focus. It is surely preferable to blood-letting in the guise of ideologically guided nation-building.

The U.S. military budget is equivalent to Pennsylvania's gross state product. Its population—uniformed, civilian and retired, contractors and dependents—would also make a mid-ranked state. You couldn't switch Wisconsin from cheese to computing in one year, or even five. There are two ways to change the Pentagon—slowly, or not at all.

That is why a four-FYDP perspective is important. It's asking too much to expect individuals and Congress to sustain such a long focus. However, it is not an unreasonable expectation for uniformed and civilian leadership, professional and appointed, and for the industrial C-suite. Indeed, that's what we pay them to do.