President Biden campaigned on his foreign policy chops honed over four decades in the Senate, but as Iran-backed proxies stepped up their attacks on American installations and service members amid growing conflicts elsewhere, the Democrat was harshly criticized Tuesday for what his leadership has wrought.

Robert O'Brien, the former Trump U.S. national security adviser, characterized Biden's global strategy as one of appeasement, which he said has lead to major conflicts in the past.

"Appeasement always buys you peace for a short period of time. But then, as Winston Churchill said, you have to drink the dregs of the bitter cup down the road, and we're drinking those dregs now," he told Fox News.

O'Brien declared the present to be "the most dangerous time for the world since 1938," and that only three years ago, the world was relatively peaceful.

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In 1938, then-United Kingdom Prime Minister Neville Chamberlain visited then-German Chancellor Adolf Hitler in Berchtesgaden and later signed an agreement with him, French Prime Minister Eduoard Daladier and Italian Prime Minister Benito Mussolini in Munich – which ceded Germany the Czech Sudetenland in exchange for his pledge to curb further imperial aspirations.

While Chamberlain declared the pact to be "peace for our time," Hitler later defied the agreement, invaded Poland, and World War II commenced.

O'Brien said that, by contrast, his own former boss' continuance of Reaganesque "peace through strength" led to the Chinese Communists being "put in a box," Russia being "deterred" from sparking aggression, and that the Republican administration was overseeing a period where Afghanistan finally appeared to be moving toward long-term relative peace.

"And now everything in the world is aflame," he said on "The Story." "And it's because President Biden moved away from a peace-through-strength posture that President Trump had, to an appeasement posture."

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Recently, Biden warned Iran and its proxies against aggressive tactics toward the United States and its allies, warning them "don't" in an September interview with CBS News host Scott Pelley.

On Tuesday, Biden told reporters he plans to respond to Iran-backed proxies killing three service members in a Jordanian drone strike, and that the chosen response has been decided upon, but declined to elaborate further.

"I do hold [Iran] responsible for supplying the weapons to the people who did it," he said.

O'Brien argued that the nexus of terror groups and Iranian proxies in the Mideast "wouldn't shoot a BB gun over our border without Iran's approval," adding that Biden should forcibly draw a "red line" and enforce it.

On the subject of deterrence, House CCP Select Committee member Mike Gallagher, R-Wis., separately told Fox News that American leadership and the citizenry alike should not doubt Chinese leader Xi Jinping's potential to wage war over the country's claim to Taiwan.

"What we've seen in the Middle East is that dictators, hostile regimes may do something that seems irrational from a Western perspective, but makes sense from their perspective, which is based solely on regime preservation," he said.

Gallagher added that in the Eastern theater, he sees that continuing to show weakness could lead to U.S. involvement in a Pacific war, which he claimed would make Ukraine "look like child's play in comparison."

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As for the Middle East, Rep. Michael Waltz, R-Fla., told "Your World" recent events prove Iran will gladly trade the lives of members of its proxy militias for Israeli lives, and that attacking the terror groups themselves will do little to deter the Ayatollah.

He underlined, however, that that does not mean the U.S must attack inside Iran, but alluded to the model of Trump ordering the attack that killed Quds Force commander Qassem Soleimani after Iran was linked to a preceding attack on the U.S. embassy in Baghdad.

"We need to hit Iranian assets themselves… that could be Soleimani's – the head of IRGC's successor" Hossein Salami.

As for responsive attacks by the U.S. thus far, Waltz said "pinprick attacks" on "warehouses in the middle of the desert" have not worked to deter aggression.

"Was it at 50 attacks on U.S. forces, 100 attacks, 150 attacks? At what point do you reevaluate your failed strategy that deterrence is failing? It's not until we have dead soldiers." Waltz said.