The special counsel, Robert S. Mueller III, has subpoenaed the Trump Organization to turn over documents, including some related to Russia, according to two people briefed on the matter. The order is the first known time that the special counsel demanded documents directly related to President Trump’s businesses, bringing the investigation closer to the president. The breadth of the subpoena was not clear, nor was it clear why Mr. Mueller issued it instead of simply asking for the documents from the company, an umbrella organization that oversees Mr. Trump’s business ventures. In the subpoena, delivered in recent weeks, Mr. Mueller...