WASHINGTON — President Obama’s new military strategy has focused fresh attention on an increasingly important threat: the use of inexpensive weapons like mines and cyberattacks that aim not to defeat the American military in battle but to keep it at a distance.

The president and his national security team predict that the security challenges of the coming decade will be defined by this threat, just as the last one was defined by terrorism and insurgency.

A growing number of nations whose forces are overmatched by the United States are fielding these weapons, which can slow, disrupt and perhaps even halt an American offensive. Modern war plans can become mired in a bog of air defenses, mines, missiles, electronic jamming and computer-network attacks meant to degrade American advantages in technology and hardware.

It is a lesson that potential enemies drew from the way American public support for the wars in Iraq and Afghanistan plummeted as armored vehicles — each costing millions of dollars — were broken and their troops killed and maimed by roadside bombs costing only a few hundred dollars apiece.