You're listening to the inquiry on the BBC World Service with me, Krupa Paddy.

Each week, one question, four expert witnesses and an answer.

It's graduation day at the end of a religious summer school in Yemen-Sada province. A class of young boys are off on a trip to a shrine.

One of them, called Osama, is filming on his phone.

The boys scatter around in the luscious cemetery playing chase weaving in and out the gravestones in a land of war they're happy

They get back on the bus jostling about and full of energy.

Moments later, most of the boys are dead.

A Saudi-led coalition air strike has hit their school bus.

Osama's phone is found among the wreckage.

The bomb that was dropped on the bus by the Saudis was made by the United States

according to analysis of the debris.

War means business and Saudi Arabia is America's single biggest customer

when it comes to buying arms.

Critics argue that Donald Trump is quietly escalating America's role in the Saudi-led war on Yemen, and some, including Congress, have begun to question the relationship between the United States and Saudi Arabia.

On this week's inquiry, we ask, the Saudi U.S. Alliance, who is in the driving seat.

Part 1, an Arabian encounter. The country had virtually no appertances of modern life. There were no telephones, there were very few schools, and there was no public

transportation or mass communication of any kind.

This is 1930s Saudi Arabia, as described by Thomas Lippman, former Middle East Bureau Chief for the Washington Post.

The country was surrounded by British colonial presence across the Middle East.

Saudi Arabia's founding monarch, King Abdulazizibenshaud, knew the United States had no colonial history in the region.

And so as he was looking for great power protection for development assistance,

the United States was an appealing target to him.

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