President Trump has decided to stonewall the Impeachment Inquiry. The New York Times article on his latest ploy starts like this:

The White House all but declared war on the House impeachment inquiry on Tuesday, intervening for the first time to block the testimony of a key witness as President Trump signaled his administration would try to starve investigators of more witnesses and documents.

The plan is to prevent witnesses from testifying and not to produce relevant documents. Remember when President Nixon had a similar plan in that he would not produce the tapes. Also remember that it did not work out so well for him.