WASHINGTON — On the morning of Jan. 21, 2017, his first full day in office, President Donald J. Trump will take a minute to settle behind the 19th-century Resolute desk, first used in the Oval Office by John F. Kennedy.

Then he will get very busy — if he follows through on his campaign promises for what he will do on his first day in office.

On Day 1, Mr. Trump has promised, he will redirect immigration enforcement, alter trade relations with China and other nations, relax restrictions on energy production, impose new rules on lobbyists, halt efforts to combat global warming, lift curbs on guns, push for congressional term limits and demand a new strategy for defeating the Islamic State. He may face some legal and procedural hurdles, but most of his Day 1 pledges involve issuing presidential directives, executive orders or memorandums that do not need legislative approval.

Although Mr. Trump and his top advisers have appeared to moderate some of his broader campaign pledges — they have suggested he might keep parts of the Affordable Care Act, delay building a wall along the border with Mexico and not appoint a special prosecutor to investigate Hillary Clinton’s emails — Mr. Trump has said nothing to indicate that he will not make good on his explicit Day 1 promises, many of which he delivered in his “Contract With the American Voter” during a speech in late October in Gettysburg, Pa.