Pick a war, any war - Trump didn't start it.
He may not have declared any new wars, but that's a 20th century way of thinking. It just isn't done like that any more.
Trump has massively extended the use of drones - currently in Afghanistan, Pakistan, Syria, Iraq, Yemen and Somalia - and exceeded Obama's totals both for overall drone strikes and civilian casualties. He also rescinded Obama's order for civilian death tolls to be recorded.
Trump has escalated the number of U.S. drone strikes overseas, and made the program even more secretive.
chicago.suntimes.com
(Bear in mind Obama was in power for twice as long.)
Then there was that time he nearly started a war with Iran, which we all seem to have forgotten about.
Continued unconditional support for the Saudis in Yemen, where they're committing atrocities, and where the US-backed anti-Houthi (I.e. anti-Iran) coalition is now working with Al-Qaeda!
Military alliance battling Houthi rebels negotiated secret deals and recruited al-Qaeda fighters, AP report says.
www.aljazeera.com
The only place I know of where Trump has de-escalated is the one place where he shouldn't have, by leaving the Kurds to the non-existent mercy of the Turkish army in northern Syria.
But yeah, apart from all that, a real force for world peace.