In 2003, the US invaded Iraq for dubious reasons to topple an objectively bad guy, Saddam Hussein. Saddam was captured. The Ba'athist regime was toppled. A Coalition Provisional Authority was established. Mission accomplished. Of course, there turned out to be no evidence of Iraqi involvement in the 9/11/01 attacks, and no weapons of mass destruction were uncovered.
Then the provisional government struggled against various groups of insurgents and rebels who saw it as a puppet regime for a foreign invader. In 2005, Nouri al-Maliki was elected Prime Minister, and he promptly alienated the Sunni minority. Presto! Civil war, or sectarian violence, if you prefer. Things quickly got messy as factions official and unofficial waged brutal war which expanded beyond the borders of Iraq.
Fast forward to late 2019. US forces officially left Iraq years ago, except they haven't. Iraq has an "official" government, but terrorists and rebels still fight it, and sometimes target the US forces that haven't left, too. The Shiite factions the US backed in the past have also suffered US drone bombings and airstikes. Oddly enough, that doesn't endear the US to them. Following more protests and attacks, the US government assassinated Iranian General Qasem Soleimani by means of a drone strike at an Iraqi airport and blamed Iran for the mess Iraq remains.
I'm sure Qasem Soleimani was an evil dude, but targeting an official of one foreign government in the territory claimed by another foreign government when at war with neither in the first place is arguably an act of war, and definitely diplomatic stupidity. If the tables were turned, and had Iran assassinated a US envoy, it would be war. Even if Iran has been cooperating with Iraqi rebels, insurgents, or the "official" government, the assassination was needless belligerence. I haven't checked a globe recently, but last I checked, Iran and Iraq shared a border. Saddam Hussein waged war against Iran. Iran taking sides in Iraqi disputes makes sense from a basic geographic and political perspective, so even if every US state department accusation against him is 100% true, this still strikes me as needless escalation of conflict. And I don't trust the people who told me Saddam had WMDs and was behind 9/11 back in 2003. I am not inclined to trust their specific justifications here, either.
This reckless act may start WW3, although more likely it will fizzle away to nothing but more lingering resentment eventually. Either way, it does not make Trump look like a visionary leader, it makes him look reckless. Remember when Trump railed against Obama's saber-rattling against Iran? The unintended consequences of Iraq, Libya, and every other war in recent decades should show how misguided belligerent foreign policy has been. We were not at war with Iran when the year began. Let's just hope that doesn't change thanks to this.