The U.S. Treasury’s decision to double the maximum size of its long-bond buybacks to $4 billion per operation from $2 billion helped ease a surge in borrowing costs after the 30-year Treasury yield climbed above 5.3% on Tuesday, its highest level since April 2007. The yield later slipped to 5.285% at Tuesday’s close and was near 5.2% on Wednesday afternoon, though it had not closed below 5% since July 6. Treasury Secretary Scott Bessent announced on Wednesday morning that the government would buy more bonds as severe market turmoil eased somewhat. The expanded buybacks, scheduled from Sept. 9 through at least Nov. 4, were viewed by some market participants as a needed response to stress in the long end of the Treasury market. John Deal of Post Oak Group said the move showed officials were acknowledging the consequences of getting debt-market policy wrong. David Kass of the University of Maryland said the operation could modestly lower benchmark yields and borrowing costs for mortgages and other consumer loans. Others said the measure addressed symptoms rather than underlying pressures. Joel Griffith of Advancing American Freedom said swapping short-term borrowing for purchases of long-term debt amounted to artificial rate suppression that could boost asset prices without addressing the causes of higher long-term yields. Economists and analysts cited persistent inflation, a divided Federal Reserve, uncertainty tied to the Iran war, erratic trade policy, heavy spending related to artificial intelligence and a rapidly rising national debt as broader sources of market unease. Federal debt topped $40 trillion on Monday, up roughly $16.5 trillion from March 2, 2020, while analysts at the Center for Strategic and International Studies estimated in June that the conflict in the Middle East had already cost the federal government between $35.2 billion and $42.5 billion. Trump downplayed the bond-market swings on Wednesday and renewed calls for lower interest rates, even as minutes from the Federal Open Market Committee’s last meeting showed that some officials believed further tightening could be needed if inflation did not ease. Consumer inflation stood at 3.4% in July, above the Fed’s 2% target, with markets awaiting the next personal consumption expenditures reading. The intervention briefly calmed the volatile market but was described as a temporary measure rather than a long-term solution. Bessent is portrayed in the source as a relatively untested Treasury secretary and a distinctive figure in Trump 2.0: Although he tries to project tough-talk bravado at cabinet meetings and in television appearances, that style appears less natural to him than to some other cabinet members.