That "started" in 2019 at the 75th Anniversary of D-Day, when he refused to go to the American cemetary because it was raining and his hair would be ruined, and in regards to the troops he said "I don't understand. What was in it for them?", and said he liked soldiers "who don't get killed".
Trump has done a terrible thing by promising to hand the Ukraine over to Putin if he's elected, and he'll let Putin do whatever he want to your NATO allies. Putin is now motivated to hold on until November, and turn his cyber criminals loose on the US election now.
This is as close to the criminal definition of "treason" as you can possibly get. Trump is making promises to Putin, if Putin helps him get elected. Just as Trump capitulated to every authoritarian despot in the world, especially China, when he was President. Trump talked tough with China but his trade war hurt the American people, and the American farmers will never recover because so many lost their farms.
China was able to find cheaper rice and grains, build new grain markets with Mexico, Chile, and Columbia, expanding their alliances and influence there with the construction of deep sea shipping ports along the Pacific coast of Central and South America, as well as the eastern coast of Africa and along the "Silk Road" trade route.
Trump got to look tough on China to his base. The American people got higher prices on Chinese goods, and the 3 straight years of bailing out US farmers, amid the highest rate of farm bankruptcies in American history.
The reason they call them "trade wars" is that there are winners, and the are losers, and the American people were not the "winners" in any of Trump's trade wars.