Special counsel Robert S. Mueller III submitted his investigation to the Justice Department in March. (Kevin Lamarque/Reuters)


Special counsel Robert S. Mueller III wrote a letter in late March complaining to Attorney General William P. Barr that a four-page memo to Congress describing the principal conclusions of the investigation into President Trump “did not fully capture the context, nature, and substance” of Mueller’s work, according to a copy of the letter reviewed Tuesday by The Washington Post.
The letter and a subsequent phone call between the two men reveal the degree to which the longtime colleagues and friends disagreed as they handled the legally and politically fraught task of investigating the president. Democrats in Congress are likely to scrutinize Mueller’s complaints to Barr as they contemplate the prospect of opening impeachment proceedings and mull how hard to press for Mueller himself to testify publicly.
At the time Mueller’s letter was sent to Barr on March 27, Barr had days prior announced that Mueller did not find a conspiracy between the Trump campaign and Russian officials seeking to interfere in the 2016 presidential election. In his memo to Congress, Barr also said that Mueller had not reached a conclusion about whether Trump had tried to obstruct justice, but that Barr reviewed the evidence and found it insufficient to support such a charge.
Days after Barr’s announcement, Mueller wrote the previously undisclosed private letter to the Justice Department, laying out his concerns in stark terms that shocked senior Justice Department officials, according to people familiar with the discussions.
“The summary letter the Department sent to Congress and released to the public late in the afternoon of March 24 did not fully capture the context, nature, and substance of this office’s work and conclusions,” Mueller wrote. “There is now public confusion about critical aspects of the results of our investigation. This threatens to undermine a central purpose for which the Department appointed the Special Counsel: to assure full public confidence in the outcome of the investigations.”
What's in the Mueller report?
A redacted version of special counsel Robert S. Mueller III's report was released to the public on April 18. Here's what's in it. 
The letter made a key request: that Barr release the 448-page report’s introductions and executive summaries, and it made initial suggested redactions for doing so, according to Justice Department officials. . . .