WASHINGTON — On Sept. 16, 1991, Angela Merkel, then a young protégé of Chancellor Helmut Kohl of Germany, watched in the Oval Office as her boss and President George Bush wrestled with the sudden collapse of the Soviet Union. Without an influx of emergency aid, Germans feared that refugees could pour across the border, threatening the stability of their newly reunified country.

Ms. Merkel shared that memory with President Trump at a summit meeting in Buenos Aires the morning after Mr. Bush’s death. Later, she told reporters, “Helmut Kohl could rely on this friend of the Germans in the White House.” If not for Mr. Bush’s sure-footed handling of those historic events, Ms. Merkel added, she “would hardly be standing here.”

With Mr. Bush’s death, a generation of Cold War leaders has passed from the stage. Of the major figures of that era, only Mikhail S. Gorbachev, the Soviet Union’s last leader, is still alive. But at 87, he is too ill to attend Mr. Bush’s funeral. Mr. Kohl died last year; even his protégé Ms. Merkel, who will go to the funeral, is now in the sunset of a political career that made her Germany’s first female chancellor.

Ms. Merkel’s reminiscences about Mr. Bush were all the more poignant, given that she was about to sit down with Mr. Trump, who grew up during the Cold War but has gleefully tried to dismantle the European and global institutions that Mr. Bush and his Cold War-vintage colleagues built.