Those bookings have fuelled a pair of federal lawsuits saying Trump violated the Constitution by taking improper payments from foreign governments.
During this period, records show, the average nightly rate at the hotel was US$768.
The lobbyists who ran the trips say they chose Trump's hotel strictly because it offered a discount from that rate and had rooms available, not to curry favour with Trump.
"Absolutely not. It had nothing to do with that. Not one bit," said Michael Gibson, a Maryland-based political operative who helped organise the trips.
Some of the veterans who stayed at Trump's hotel say they were kept in the dark about the Saudis' role in the trips. Now, they wonder whether they were used twice over: not just to deliver someone else's message to Congress but also to deliver business to the Trump Organisation.
"It made all the sense in the world, when we found out that the Saudis had paid for it," said Henry Garcia, a Navy veteran from San Antonio who went on three trips. He said the organisers never said anything about Saudi Arabia when they invited him.
He believed the trips were organised by other veterans, but that puzzled him, because this group spent money like no veterans group he'd ever worked with. There were private hotel rooms, open bars, free dinners. Then, Garcia said, one of the organisers who had been drinking minibar champagne mentioned a Saudi prince.
"I said, 'Oh, we were just used to give Trump money,' " Garcia said.
The Washington firm Qorvis/MSLGroup, which has long represented the Saudi Government in the United States, paid the organisers of the "veterans fly-in" trips, according to lobbying disclosure forms. The firm declined to comment.
The Saudi Embassy did not respond to questions for this story. Trump hotel executives, speaking on the condition of anonymity to discuss their clients, said they were unaware at the time that Saudi Arabia was ultimately footing the bill and declined to comment on the rates they offer to guests.
The existence of the Saudi-funded stays at Trump's hotel were reported by several news outlets last year. But reviews of emails, agendas and disclosure forms from Saudi lobbyists and interviews this northern autumn with two dozen veterans provide far more detail about the extent of the trips and the organisers' interactions with veterans than have previously been reported.
That reporting showed a total of six trips, during which the groups grew larger after the initial visit and the stays increased over time. The Post estimated that the Saudi Government paid for more than 500 nights in Trump hotel rooms, based on planning documents and agendas given to the veterans and conversations with organisers.
These transactions have become ammunition for plaintiffs in two lawsuits alleging that Trump violated the Constitution's foreign emoluments clause by taking payments from foreign governments. Yesterday, the attorneys general in Maryland and the District subpoenaed 13 Trump business entities and 18 competing businesses, largely in search of records of foreign spending at the hotel.
Earlier this year, the Trump Organisation donated about US$151,000 to the US Treasury, saying that was its amount of profits from foreign governments, without explaining how it arrived at that number. The Justice Department, defending Trump in the lawsuits, says the Constitution doesn't bar routine business transactions.
Next year, the transactions will also face scrutiny from the House's new Democratic majority. Democrats have said they want to understand Trump's business connections with the Saudi Government in the aftermath of the killing of Post contributing columnist Jamal Khashoggi in the Saudi Consulate in Turkey.
"Foreign countries understand that they can curry favour with the President by patronising his businesses," said Congressman Adam Schiff, D, who will lead the House Intelligence Committee next year. "It presents a real problem, in that it may work."
The White House declined to comment.
