Liverpool had not led all season until tonight, but they started with a clear desire to set that right, and they were in front at Portman Road in the sixth minute.
Having seen a possible transfer collapse late on in the window, Cody Gakpo looked as sharp as ever, and his neat through ball to Isak was finished emphatically by the Swede at the near post.
By the ninth minute, the pair had combined again to double the advantage, Isak teasing Jacob Greaves and then guiding the ball beyond Kjell Scherpen after running onto a delightful outside-of-the-boot pass.
Dominik Szoboszlai then tested Scherpen with a stinging strike from the edge of the box, the first of three such efforts which the goalkeeper had to deal with before the break.
The hosts belatedly responded with some sort of attacking threat, and Leif Davis should really have added to last week’s goal at Old Trafford with a header at the back post, which he sent wide.
But the Tractor Boys looked constantly vulnerable at the back, and Isak thought he had a first-half hat-trick following an inch-perfect Florian Wirtz pick-out, only to be denied by a narrow offside call.

The visitors almost made a lightning start to the second half as well, and Alexis Mac Allister had a golden chance to convert from a Szoboszlai corner, heading his effort tamely at Scherpen.
Andoni Iraola was forced to endure a needless scare when Jeremy Jacquet picked up a cheap yellow card and then appeared to go in clumsily on Emersonn just moments later, but referee Darren England didn’t even award a free kick.
There was to be no hat-trick for Isak, who was withdrawn just after the hour mark, but that set the stage for the arrival of new signing Bradley Barcola, who got supporters off their seats in the away end with a slaloming run shortly after his introduction.
VAR then looked set to award a penalty after Szoboszlai was felled in the box, but the Hungarian was offside in the build-up, leaving the Suffolk side just about still in the contest.
But Ipswich could do very little with their reprieve and never really looked like changing the result, although a deflected Jack Clarke strike briefly had Alisson Becker worried.
Victory means Liverpool avoid going seven games without a win for only the second time in their history, while extending a sequence of 21 games unbeaten against newly-promoted teams (W16, D5).
After a dream start against Sunderland, Ipswich have now been dealt a harsh dose of PL reality, losing their last two games by a 7-2 margin.
Flashscore Man of the Match: Virgil van Dijk (Liverpool)
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