(Want to get this briefing by email? Here\u2019s the sign-up.) Good morning, We\u2019re covering the roots of the recent national security shake-up, a new angle to China\u2019s surveillance state, and a comeback for Tiger Woods. Top aide pushed for Homeland Security purge President Trump insisted over the weekend that he was \u201cnot frustrated\u201d by the situation at the southwestern border, but as his administration seeks sweeping changes, he has targeted his highest-ranking immigration officials. The removal of top officials at the Department of Homeland Security came after months of clashes involving Stephen Miller, the White House adviser and architect of Mr. Trump\u2019s immigration agenda. Mr. Miller and others have pressed for implementing policies that current and former officials have called legally questionable, impractical, unethical or unreasonable. Another angle: In addition to what he has said are the dangers of immigration, Mr. Trump has played on fears of Muslims. He is likely to resurrect that theme during his re-election campaign and has apparently picked a specific target: Representative Ilhan Omar, a Minnesota Democrat who is one of the first Muslim women elected to Congress. Looking ahead: A redacted version of the special counsel\u2019s report is expected to be released this week. Mr. Trump\u2019s plan, aides say, is to act as if the report itself is extraneous to the attorney general\u2019s summary, which the president has said exonerated him. China already maintains a surveillance net, including tracking people\u2019s DNA, in the western region of Xinjiang, home to many of the country\u2019s 11 million Uighurs. But the new systems, previously unreported, extend that monitoring to the rest of the country. How we know: Five people with direct knowledge of the systems, who requested anonymity because they feared retribution, described them to The Times. We also reviewed databases used by the police, government procurement documents and advertising materials distributed by the companies that make the systems. Seeking refuge from climate change Nowhere is immune from global warming, but projections suggest that the Great Lakes area will be one of the few places in the U.S. where the effects may be more easily managed. Consider Duluth, Minn., which is relatively cool, is mostly protected from the effects of sea level rise and has an abundance of fresh water. A climate adaptation expert at Harvard thinks the city and others like it might be ideal for climate migrants. Another angle: Rising temperatures and increasingly unpredictable weather have been ruining harvests in Central America and adding to the surge of families migrating to the U.S., farmers and scientists say. A victory for the ages for Tiger Woods The 43-year-old ended a decade-long major championship drought on Sunday, winning his fifth Masters title. \u201cIt fits,\u201d he said as he put on the winner\u2019s green jacket. The victory gave him his 15th major tournament triumph, three behind Jack Nicklaus\u2019s record. Column: Woods rediscovered his confidence on Sunday and his ability to intimidate the competition, our columnist writes. Background: For Woods, a marital dispute led to a car accident in 2009 and a succession of lurid tabloid headlines. On the golf course, back injuries led to a series of operations and an addiction to painkillers. The Times profiled him last year. If you have 8 minutes, this is worth it Canada\u2019s feminist government For months, the government of Prime Minister Justin Trudeau has been consumed by controversy after the resignation of the attorney general, Jody Wilson-Raybould, second from left above. She accused Mr. Trudeau\u2019s office of inappropriately pressuring her in a criminal case. For Mr. Trudeau, whose cabinet by design contains equal numbers of women and men, the episode has also raised questions about whether his government is living up to its billing as a feminist administration. Here\u2019s what else is happening Google\u2019s dragnet: One of our most popular articles over the weekend was about how investigators are using location information from the tech giant to find suspects and witnesses near crimes, sometimes snaring the innocent. ISIS kidnapping: A rift emerged today between New Zealand\u2019s government and the Red Cross over the humanitarian organization\u2019s decision to identify a New Zealand nurse who was kidnapped by the Islamic State five years ago \u2014 and who her employer believes could still be alive. Electric bike problems: Bike-sharing companies owned by Lyft have pulled electric models from New York, San Francisco and Washington because of braking problems. Tax deadline: Personal income tax returns are due today. It may not feel like it from your refund (or lack of one), but you probably got a tax cut last year. Now is the time to check your paycheck withholdings for next year\u2019s return. Snapshot: Above, part of the open-air art installation \u201cDetr\u00e1s del Muro,\u201d or \u201cBehind the Wall,\u201d along the Malec\u00f3n in Havana on Sunday. The 13th Biennial in Cuba\u2019s capital began this weekend, with works by more than 300 contemporary artists from 52 countries. Boston Marathon: The 123rd edition of the event is today. Sarah Sellers, the runner-up in 2018, will be back this year, with a rare ambition to be an elite runner and work a practically full-time job. \u201cGame of Thrones\u201d recap: The eighth and final season of the show began on HBO on Sunday. Here\u2019s our review. What we\u2019re reading: This article in Science News. \u201c\u2018Dumbo\u2019 is a delightful movie, but an elephant is never going to fly by flapping its ears,\u201d says Michael Roston, a science editor. \u201cThis fun article by Bethany Brookshire examines the anatomical obstacles.\u201d Now, a break from the news Go: The musical \u201cBeetlejuice\u201d is now in previews on Broadway. Here\u2019s how the eye-popping set came together. Smarter Living: There are scientifically proven ways to increase your memory power. Consolidate information by retreating to a dark, quiet room for 10 minutes of inactivity (but not sleep). And you can increase your ability to retrieve memories by quizzing yourself on them, or sharing them out loud. And we look at the benefits of sharing \u2014 whether triumphs, photographs or difficulties \u2014 in person rather than on social media. And now for the Back Story on \u2026 The \u2018Wiki\u2019 in \u2018WikiLeaks\u2019 With the arrest last week of its founder, Julian Assange, WikiLeaks is back in the headlines. \u201cLeaks\u201d is obvious for the name of the anti-secrecy organization, which started in 2006, but where does \u201cwiki\u201d come from? In 1995, the computer programmer Ward Cunningham introduced the first wiki, a website that\u2019s collaboratively produced by users. He called it WikiWikiWeb, after the Hawaiian word for \u201cquick,\u201d which he had picked up from the name of an airport shuttle in the islands. The word was later adopted by Wikipedia, the online encyclopedia that started in 2001, and it was added to the Oxford English Dictionary in 2007. The wiki isn\u2019t Mr. Cunningham\u2019s only contribution to modern online life. He also gave his name to Cunningham\u2019s Law, the idea that the best way to find the correct answer on the internet isn\u2019t to ask a question, but to post the wrong answer. That\u2019s it for this briefing. See you next time. \u2014 Chris Thank youTo Mark Josephson, Eleanor Stanford and James K. Williamson for the break from the news. Chris wrote today\u2019s Back Story. You can reach the team at firstname.lastname@example.org. P.S.\u2022 We\u2019re listening to \u201cThe Daily.\u201d Today\u2019s episode is about Julian Assange.\u2022 Here\u2019s today\u2019s mini crossword puzzle, and a clue: Newlywed\u2019s new relative (5 letters). You can find all our puzzles here.\u2022 The Research and Development team at The Times has launched the 5G Journalism Lab to explore how higher and faster bandwidth might unlock new ways to tell stories.