Macron said that the alliance was experiencing what he called brain death.

You just can't go around making statements like that about NATO.

It's very disrespectful.

Nobody needs NATO more than France.

As tensions within the alliance keep playing up publicly, the North Atlantic Treaty Organization is having a bit of an identity crisis.

I don't think we're looking at the imminent breakup of NATO.

What we're seeing at the minute is a debate about what the alliance is gonna be in the next 70 years.

The big question for NATO today is, does it need to change to remain relevant?

NATO's banner flies proudly.

NATO has evolved over time, from a 12-member group formed in 1949 and focused on protecting Europe from the Soviet Union to the 29-member global security organization it is today, conducting a range of security missions around the world.

The alliance has always been based on the same principle of a collective defense.

An attack on one member country is an attack on all allies.

The benefits are enormous.

You're in NATO and your country is attacked, then all of the other countries are bound by treaty to come to your defense as well.

Here's where things get tricky.

The concept of a collective defense rests on the idea that everyone is on the same page about who the enemy is.

In the early days, the enemy was clear, the Soviet Union.

Since the foundation of the North Atlantic Treaty Organization, the communists have gained not one foot of new territory in Europe.

Today, it's not so simple.

I think, though, that the main fundamental shift is this big question that Macron has brought up, so is Russia our enemy?

No, is his answer.

Is China our enemy?

No, is his answer.

I suppose, then, the question from the other allies is, well, what are they?

One way the organization is evolving is by shifting some of its resources to things like cybersecurity and space.

But that collective commitment to defense costs money, and money has become a big reason for tensions.

It's not right to be taken advantage of on NATO and also, then, to be taken advantage of on trade, and that's what happens, and we can't let that happen.

The issue has been called burden-sharing or the idea that member countries should all pay their fair share.

Fair burden-sharing underpins everything that we do.

The U.S. has been seen as the leader of NATO, and it spends more on defense than the other members, which President Trump and others say is unfair.

NATO members must finally contribute their fair share and meet their financial obligations.

For context, Trump isn't the first president to raise the issue.

Everybody's gotta step up, and everybody's gotta do better.

But he is the first to suggest he might not defend some NATO allies if they don't pay up.

In 2014, NATO countries formally agreed to spend 2% of their GDP on defense by 2024.

In 2016, only four of the 29 allies were spending that much.

Now, the White House says that number's up to nine.

Still, there's no penalty if countries don't make the guideline and not everyone is expected to reach the 2% by 2040.

There's been an impetus again to start investing in defense.

It's very expensive, you have to take money away from things like hospitals and schools, which is not necessarily popular, so that's been difficult for governments.

Different countries have different priorities.

Some are more willing to invest in defense than others, and those riffs are a manifestation of fundamental disagreements over how the alliance should operate.

Just take Trump's decision to pull U.S. troops out of Syria.

Turkey, which is also a NATO member, moved into the region.

This all happened without consulting NATO allies, and NATO members were split on how to respond.

NATO plays things very cool.

They are an alliance of 29 countries.

Over the years, NATO's become very good at balancing the interests of all of those countries.

Certainly, Macron's comments have shaken up what would've been, what they hoped to be a more sedate affair.