The game at a glance
Man of the match: Mario Mandzukic (Croatia), The man who ensured that Croatia plundered the chances when they needed them and his second goal was a beauty.
Sean St Ledger's headed goal bridged a yawning, decade-long period of absence from major tournaments and was celebrated with a wonderful release of emotion that reverberated through the crowd and offered a slim hope Ireland could eke out a result.
Two goals either side of half-time from the Croatians ended this as a contest. Ireland somehow needed to get to the break level or at least get a decent foothold at the start of the second half. That they managed neither fatally undermined their chances.
Ireland have rarely been punished like this at a major tournament; Trapattoni's honeymoon period as Ireland manager is certainly over and if the rest of the competition continues like this, few would tolerate him staying in the position.
Over 23,000 Irish fans, outnumbering their Croatian counterparts by two to one, were in fine fettle and sang their hearts out, even when the final whistle confirmed their deep disappointment at a wretched result and performance.
Bjorn Kuipers oversaw Ireland's sleepy play-off win against Estonia but this was a tad more controversial and he felt Trapattoni's wrath at half-time and afterwards, particularly after denying Robbie Keane a penalty.
Yellow cards: Croatia 1 (Krancjar 19); Ireland 1 (Andrews 43).
Red cards: Croatia 0 Ireland 0.
Shots on target: Croatia 8 Ireland 4.
Corners: Croatia 6 Ireland 2.
Ireland play Spain in their second Group C encounter (7.45 Irish time) in Gdansk on Thursday; earlier that day, Croatia return to Poznan to play Italy (5.0 Irish time).