The nation's military strategy has been permanently altered to focus on the long war ahead to defeat non-state actors and new forms of warfare with state adversaries, the Pentagon's top officer said.

"We are more likely to face prolonged campaigns than conflicts that are resolved quickly … that control of escalation is becoming more difficult and more important … and that as a hedge against unpredictability with reduced resources, we may have to adjust our global posture," Joint Chiefs of Staff Chairman Gen. Martin Dempsey said Wednesday, releasing the 2015 National Military Strategy.

The strategy is one of a handful of core documents that are released by the president, the defense secretary and chairman that guide the nation's defense strategic priorities, and guide how the military will posture itself to execute that strategy.

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This new strategy, the first released by the Pentagon since 2011, takes on a decidedly darker hue than its predecessor. Dempsey warns that demands on the nation's military and populace against metastasizing violent extremist organizations like the Islamic State will likely mean "a difficult future."

In the 2011 National Military Strategy, the military still spoke of the war against non-state actors as "a challenging new era."

In 2015, the strategy asserts that "the application of the military instrument of power against state threats is very different than the application of military power against non-state threats."

"We are blessed to be able to count on the young Americans who choose to serve, to live an uncommon life, and to defend their fellow citizens."

Also notable in the 2015 strategy is the emergence of "hybrid warfare" — where war is fought by intermediaries backed by states that don't necessarily acknowledge they are behind the actions, for example Russia's equipping and direct support of militants in eastern Ukraine.