Stockholm, which rose 1.4 percent on Tuesday, was once again hit by a sharp surge on the New York stock exchanges on Tuesday evening.
The development comes after a bleak March and after Trump stated that he expects the country's military "to leave Iran within two to three weeks."
On Wednesday, he also announced that Iran had asked for a ceasefire, which Tehran soon denied.
Trump is scheduled to give a speech to the nation about the war on Thursday night, local time in Sweden.
On the OMXS30 list of the most traded stocks in Stockholm, the defense group Saab performed best, up 7.4 percent, after Trump said in an interview that he wants to reconsider NATO membership.
Mining giant Boliden, which has been falling sharply for some time, rebounded and rose 5.8 percent.
Engineering companies such as Sandvik, ABB, Atlas Copco and Alfa Laval also had a good day.
Construction company Skanska fell 3.7 percent when the share traded ex-dividend for the day.
Only four of the 30 stocks on the large-cap list fell.
The oil price fell slightly during the day. At the close in Stockholm, a barrel of North Sea oil cost 101.6 U.S. dollars per barrel. American WTI oil was 99.4 U.S. dollars.
The stock exchanges in Frankfurt, London and Paris also rose sharply. The three major indexes in New York are also clearly in the red.
With Wednesday's rise, the Stockholm Stock Exchange is back in the black since the turn of the year, up 0.3 percent.
