Our colleague Greg Ip, chief economics commentator, is a bit of a history buff.

And over the weekend, as President Donald Trump talked about why the U.S. captured Venezuela's president, Nicholas Maduro,

something in particular stood out to him.

For as long as you and I can remember, when presidents went into another country, they always had high-minded reasons, you know, oh, we need to restore democracy.

He's threatening his neighbors.

No one, friend or foe, should doubt our desire for peace.

When George H.W. Bush freed Kuwait from Iraq in 1991.

And no one should underestimate our determination to confront aggression.

When George W. Bush went into Iraq in 2003, they explicitly disavowed any interest in taking Iraq's oil.

We have no ambition in Iraq except to remove a threat

and restore control of that country to its own people.

In contrast, Trump has made it clear that a big motivation

for carrying out his operation in Venezuela

is because of a desire for a highly prized commodity, oil.

The oil companies are going to go in, they're going to spend money.

We're going to take back the oil that, frankly, we should have taken back a long time ago.

The Trump administration says its primary reason for arresting Maduro was his involvement

in drug trafficking.

In court earlier this week, Maduro pleaded not guilty.

But Greg says the U.S. action in Venezuela, and the way Trump has been talking about it,

represent a generational shift in the way American presidents think about foreign policy.

In his view, American greatness does not flow so much from values, such as the promotion of democracy and freedom.

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