Republic of Ireland's prospects of progressing beyond the group stages of Euro 2012 suffered a huge blow as they were undone by a clinical and classy Croatia in Poznan.
Mario Mandzukic's header eluded Shay Given to put the Croatians ahead inside three minutes, but a spirited Irish response saw Sean St Ledger equalise.
Nikica Jelavic's delightful dinked finish made it 2-1 before the break.
And a second Mandzukic header, which went in off Given, sealed the win.
There can be few Irish complaints about the final outcome with the superior technical quality of Croatia eventually telling in a frantic and attack-minded Group C encounter at the Municipal Stadium.
The Republic have been consistently accused of being negative and unadventurous under their veteran manager Giovanni Trapattoni.
But, with a feeling victory was crucial in their opening game of an exceedingly tough looking group where Italy and Spain still await, it was fully expected they would adopt a slightly more attacking approach than they displayed during a dogged but unspectacular qualification campaign.
Spain's 1-1 draw with Italy in the Group C opener possibly added even greater encouragement to play a little more expansively.
As it transpired, a disastrous start meant Trapattoni's team had little option as the Croatians went ahead with their first attack when the Irish failed to clear a corner.
Mandzukic's goal was more than a little fortunate, the big striker making the most of a deflection off the back of Stephen Ward to crane his neck and nod the ball into the corner from 12 yards via the hands of a wrong-footed Given.
The Irish response was no means gung-ho, but the 73-year-old Italian seemed to get the balance - and his tactics - spot on, and the Republic were deservedly level after 19 minutes.
The midfield played with more freedom than the solid defensive displays which saw them defeated just once on their way to the finals and has brought about a 14-game unbeaten run with 11 clean sheets.
Aiden McGeady was the main man to benefit and it was his inviting, inswinging free-kick which allowed St Ledger to get around the back of Vedran Corluka and bundle the ball in off his shoulder.
A second whistle could be heard in the crowd as the set-piece was delivered but it made no difference and the goal sparked a 'full Poznan' from the hordes of Irish fans - every bit as impressive as those witnessed by the Manchester City supporters who adopted the celebration after a visit to the stadium in 2010.
By now the game was as open and entertaining as anything seen so far in the tournament.
Robbie Keane's inventiveness, the tireless running of Damien Duff and Kevin Doyle, and the trickery of McGeady always looked like creating a goal.
But the Croatians were playing with the greater guile and craft and, after recovering from the setback of surrendering their early lead, they started to dominate possession and create chances.
Tottenham playmaker Luka Modric was the instigator, orchestrating play from increasingly advanced positions and picking passes at will.
Ivan Perisic twice went close with majestic long-range volleyed efforts and Modric hit a well-struck first-time 25-yard effort straight at Given.
At the other end, McGeady whipped in another decent free-kick and Keane almost got in on goal after a defensive mix-up.
But Croatian quality started to show and the Irish defence buckled under the pressure.
Everton striker Jelavic made it 2-1 just before the interval with a clever chipped finish after a sliced Ward clearance landed at his feet.
And the game was as good as over four minutes after the restart when a second Mandzukic header found the back off the net, this time via the head of the unlucky Given as the ball bounced back into play off the post.
The Irish regrouped and were denied what appeared a blatant penalty when Gordon Schildenfeld went through the back of Keane on the edge of the box.
However, even though the Republic's luck had deserted them, Croatia continued to look in control, technically superior and able to step up the pace if required.
They had chances to extend their lead, the best of which saw a fabulous sweeping move almost end with Ivan Rakitic firing just wide from 20 yards.
The Irish also had opportunities in the closing stages, but Keith Andrews screwed two shots wide and wasted a good headed chance.
But the Irish could not drag themselves back into the game and now face reigning European champions Spain on Thursday, needing at least a point to keep alive their chances.
Rep of Ireland: Given, O'Shea, St. Ledger, Dunne, Ward, McGeady (Cox 54), Whelan, Andrews, Duff, Doyle (Walters 53), Keane (Long 75).
Subs Not Used: Westwood, Kelly, McShane, Gibson, Hunt, O'Dea, Green, McClean, Forde.
Goals: St. Ledger 19.
Croatia: Pletikosa, Srna, Corluka, Schildenfeld, Strinic, Vukojevic, Rakitic (Dujmovic 90), Modric, Perisic (Eduardo 89), Mandzukic, Jelavic (Kranjcar 72).
Subs Not Used: Kelava, Simunic, Buljat, Pranjic, Badelj, Vrsaljko, Kalinic, Vida, Subasic.
Booked: Modric, Kranjcar.
Goals: Mandzukic 3, Jelavic 43,Given 49 og.
Referee: Bjorn Kuipers (Holland).