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The most dangerous moments in foreign affairs often come after a major power seeks to reassert its lost deterrence.

The United States may be entering just such a perilous transitional period.

Rightly or wrongly, China, Iran, North Korea, Russia and Middle East-based terrorists concluded after 2009 that the U.S. saw itself in decline and preferred a recession from world affairs.

In that void, rival states were emboldened, assuming that America thought it could not -- or should not -- any longer exercise the sort of political and military leadership it had demonstrated in the past.

Enemies thought the U.S. was more focused on climate change, United Nations initiatives, resets, goodwill gestures to enemies such as Iran and Cuba, and soft-power race, class and gender agendas than on protecting and upholding longtime U.S. alliances and global rules.

In reaction, North Korea increased its missile launches and loudly promised nuclear destruction of the West and its allies.

Russia violated its obligations under the Intermediate-Range Nuclear Forces Treaty and absorbed borderlands of former Soviet republics.

Iran harassed American ships in the Persian Gulf and issued serial threats against the U.S.

China built artificial island bases in the South China Sea to send a message about its imminent management of Asian commerce.

In Syria and Iraq, the Islamic State killed thousands in medieval fashion and sponsored terrorist attacks inside Western countries.

Amid such growing chaos, a return to former (and normal) U.S. deterrence would inflame such aggressors and be considered provocative by provocateurs.

Accordingly, we should remember a few old rules for these scary new crises on the horizon.

1. Avoid making verbal threats that are not serious and backed up by force. After eight years of pseudo-red lines, step-over lines, deadlines and "game changers," American ultimatums without consequences have no currency and will only invite further aggression.

2. The unlikely is not impossible. Weaker powers can and do start wars. Japan in December 1941 attacked the world's two largest navies based on the false impression that great powers which sought to avoid war did so because they were weak. That current American military power is overwhelming does not mean delusional nations will always agree that it is so -- or that it will be used.

3. Big wars can start from small beginnings. No one thought an obscure Austrian archduke's assassination in 1914 would lead to some 18 million dead by 1918. Consider any possible military engagement a precursor to far more. Have a backup plan -- and another backup plan for the backup plan.

4. Do not confuse tactics with strategy. Successfully shooting down a rogue airplane, blowing up an incoming speedboat or taking an ISIS-held Syrian city is not the same as finding a way to win and end a war. Strategic victory is time-consuming and usually involves drawing on economic, political and cultural superiority as well as military success to ensure that a defeated opponent stays defeated -- and agrees that further aggression is counterproductive.

5. Human nature is unchanging -- and not always admirable. Like it or not, neutrals more often flock to crude strength than to elegant and humane weakness.

6. Majestic pronouncements and utopian speechifying impress global elites and the international media, but they mean nothing to rogue nations. Such states instead count up fleets, divisions and squadrons -- and remember whether a power helps its friends and punishes its enemies. Standing by a flawed ally is always preferable to abandoning one because it can sometimes be bothersome.

7. Public support for military action hinges mostly on perceived success. Tragically, people will support a dubious but successful intervention more than a noble but bogged-down one. The most fervent prewar supporters of war are often the most likely to bail during the first setback. Never calibrate the wisdom of retaliating or intervening based on initial loud public enthusiasm for it.

8. War is a harsh distillery of talent. Good leaders and generals in peace are not necessarily skilled in conflict. They can perform as badly in war as good wartime generals do in peace. Assume that the commanders who start a war won't be there to finish it.

9. War is rarely started by accident and far more often by mistaken calibrations of relative power. Flawed prewar assessments of comparative weakness and strength are tragically corrected by war -- the final, ugly arbiter of who really was strong and who was weak. Visible expressions of military potential, serious and steady leadership, national cohesion and economic robustness remind rivals of the futility of war. Loud talk of disarmament and a preference for international policing can encourage foolish risk-takers to miscalculate that war is a good gamble.

10. Deterrence that prevents war is usually smeared as war-mongering. Appeasement, isolationism and collaboration that avoid immediate crises but guarantee eventual conflict are usually praised as civilized outreach and humane engagement.

Finally, it is always better to be safe and ridiculed than vulnerable and praised.