Brett McGurk is a CNN global affairs analyst who served in senior national security positions under Presidents George W. Bush, Barack Obama, Donald Trump and Joe Biden.

As a candidate, Donald Trump promised to end the Ukraine war on his first day in office and swiftly bring the Gaza war to a close as well. Now more than six months into his presidency, peace on both fronts appears further away than ever.

In Gaza, talks for a ceasefire and hostage deal that had shown promise only a few weeks ago broke down, and the humanitarian situation is catastrophic. In Ukraine, repeated diplomatic approaches were answered by Russia with its largest air attacks to date.

What happened? And what can be done now?

There is no more difficult diplomatic task than ending a war, and Trump is not the first president to learn this lesson the hard way: