Although there really is no difference between Trump and Biden but you are forgotting that on January 2020 he ordered a terrorist attack that killed an Iranian general (with his Iraqi counterpart) on an official mission to Iraq to discuss the operations to eliminate the remainder of US backed ISIS terrorists inside Iraq.

Iran started a series of retaliations as the response to that act of terror that included elimination of various US military officers that were involved in that terrorist attack. But the main one that could be called "being at the brink" was to carry out what Pentagon calls the largest ballistic missile attack to that date; it was on 2 US military bases with over a hundred US servicemembers eliminated and nearly a thousand incapacitated in a blinking of an eye.

If Trump hadn't been scared shitless of Iran's military power back in 2020 and had tried showing any kind of aggression, a World War would have started...

Washington and Tehran both confirmed that Iran was the source of the missiles. The extent the damage was unclear.

Iran's Supreme Leader Ayatollah Ali Khamenei said the strikes were a "slap in the face" to the U.S. and not sufficient retaliation for the killing of Soleimani, a top general, last week.

In a White House address, President Donald Trump said: "No Americans were harmed in last night's attack by the Iranian regime. We suffered no casualties. Our great American forces are prepared for anything. Iran appears to be standing down."