Veterans of past administrations could not recall a precedent for a president meeting alone with an adversary and keeping so many of his own advisers from being briefed on what was said. When they meet with foreign leaders, presidents typically want at least one aide in the room — not just an interpreter — to avoid misunderstandings later. Memorandums of conversation, called Memcons, are drafted and details are shared with officials who have reasons to know what was said…

“If any president would have wanted witnesses and protection, it ought to have been Donald Trump,” said Richard N. Haass, the president of the Council on Foreign Relations and adviser to four presidents, most recently as President George W. Bush’s State Department policy planning director. “And yet he chose not to, and that adds fuel to the fire that something here is not right.”…

Mr. Trump’s meeting with Mr. Putin that day lasted more than two hours. Afterward, Mr. Trump took his interpreter’s notes and instructed the interpreter not to brief anyone. Mr. Tillerson told reporters that the leaders discussed everything from Syria to Ukraine, but he also described “a very robust and lengthy exchange” on the election hacking…

The day after the two meetings, as Mr. Trump was on Air Force One taking off from Germany heading back to Washington, he telephoned a Times reporter and argued that the Russians were falsely accused of election interference. While he insisted most of the conversation be off the record, he later repeated a few things in public in little-noticed asides.