President Donald Trump mocked France's war record in a Tuesday-morning tweet that again waved the idea of the US pulling out of, or modifying its relationship to, the NATO military alliance.

French President Emmanuel Macron has long pushed for a European army separate from NATO, and he recently said the army was needed to protect against the US in some capacities.

Trump immediately took offense to the suggestion, calling it "very insulting."

France fought valiantly in World War I but got steamrolled in World War II. Since then, France's army has emerged as world-class and among the best in Europe.

President Donald Trump mocked France's war record in a Tuesday-morning tweet that again waved the idea of the US pulling out of, or modifying its relationship to, NATO.

French President Emmanuel Macron has long pushed for a European army separate from NATO, the global military alliance that includes the US and Canada and has sought to secure the continent against Russian aggression that has grown since the end of World War II.

Spurred by the US's withdrawal from the Intermediate-Range Nuclear Forces Treaty, which eliminated a category of nuclear weapons and almost denuclearized the continent, Macron renewed his calls to break away from depending on US military might.

"We have to protect ourselves with respect to China, Russia, and even the United States of America," Macron said on November 6. Macron later clarified his comments about protecting Europe from the US, saying they focused mainly on cybercrime and building domestic defense industries that didn't need to buy or invest in US arms.

But Trump took offense to Macron's suggestion, calling it "very insulting."

"Emmanuel Macron suggests building its own army to protect Europe against the U.S., China and Russia," Trump tweeted on Tuesday. "But it was Germany in World Wars One & Two - How did that work out for France? They were starting to learn German in Paris before the U.S. came along. Pay for NATO or not!"

The French war record

The Battle of Verdun in World War I. General Photographic Agency/Getty Images

Read more: Trump torches allies, threatens NATO pullout after tense World War I memorial trip to Paris

While France has long borne shame for its quick defeat to and partial collaboration with the Nazis during World War II, the French fought an extremely dedicated fight in World War I.

World War I saw France lose nearly 1.4 million troops and an additional 300,000 civilians.

In World War II, France lost just over 200,000 troops and another 350,000 civilians after being taken by surprise by Hitler's Nazi war machine. France declared war on Germany in 1939, while the US joined the fight two years later after the Japanese attack on Pearl Harbor.

France has long faced ridicule for its World War II performance, despite a complicated and extremely taxing war effort that consumed nearly the entire continent before the D-Day landings.

Once Allied forces landed back on the continent, French troops rejoined the war effort and fought shoulder-to-shoulder to end Nazi occupation across Europe.

Plus, it was with French help that the US defeated the British during the American Revolutionary War.

Today, France's military stands among Europe's best. Only France has a nuclear-powered aircraft carrier, and the country has contributed greatly to anti-terrorism and anti-extremist fighting across the Middle East and Africa.

Germany keeps a relatively small military and has resisted heavy spending or foreign operations.

On Monday, Trump also seemed to float the possibility of pulling out of NATO, urging European countries to spend more on defense as long as they maintained trade surpluses with the US.

Trump and Macron descend into outright confrontation

Trump and Macron met on Saturday. Christophe Petit Tesson/Pool via AP

Read more: France's army appears to troll Trump for missing a World War I memorial because of rain

Trump and Macron, initially engaged in what the media widely labeled a "bromance," have sharply descended into open confrontation and hostility in the past few weeks.

Trump responded to Macron's calls for a European army as an insult before arriving in Paris over the weekend to memorialize the 100th anniversary of the end of World War I.

The pair shared a white-knuckled handshake on Trump's arrival — seemingly in a sign of things to come.

Macron openly rebuked Trump's political philosophy in a speech on Sunday, in which he called nationalism — something Trump has embraced — a betrayal of patriotism and moral values.

But the specifics of Macron's plan for a European army remain unclear, as European nations have very different foreign-policy agendas and interests.