World Cup Super 8, Barbados:
Ireland 243-7 (50 ovs) bt Bangladesh 169 (41.2 ovs) by 74 runs
Ireland captain Johnston wrapped up victory with the final wicket
Ireland claimed the scalp of a second Test-playing nation at the World Cup as they defeated Bangladesh by 74 runs in their Super 8 encounter in Barbados.
Bangladesh were set 244 to win but lost wickets at regular intervals.
Mohammad Ashraful (35) played some fine shots but when he went with the score on 102-5 defeat was inevitable.
Earlier, William Porterfield grafted his way to an invaluable 85 while Kevin O'Brien (48) and Trent Johnston (30) supplied some late Irish fireworks.
The match was supposed to be one of the highlights of the Super 8 stage, with Pakistan and India coming head to head at the splendidly rebuilt Kensington Oval.
But instead of the two Asian giants, who crashed out at the group stage, it was left to the two bottom-ranked teams remaining in the tournament to try and put on a show.
After winning the toss and batting, the Irish faced a testing new-ball spell from Shahadat Hossain and Mashrafe bin Mortaza on a wicket featuring good pace and bounce.
Porterfield rode his luck, twice edging short of second slip and being dropped off a no-ball, but Bangladesh could not make the breakthrough.
And Ireland, whose highest opening partnership in the tournament had been just seven, patiently worked their way to 32-0 after 10 overs.
Porterfield, who should have been caught and bowled by Mohammad Rafique in the 17th over, was the more positive of the openers.
Jeremy Bray, who started the tournament with an unbeaten 115 against Zimbabwe but followed it up with scores of 0,0,1,1, was content to accumulate, and they put on a vital 92 before the first wicket fell in the 26th over.
Porterfield, on 49, called Bray through for a single and the non-striker's hesitation was enough to cost him his wicket as he was run out by Saqib al Hasan for 31.
New batsman Eoin Morgan was soon run out as well as the pressure being applied by Bangladesh's trio of left-arm spinners forced Ireland to chance their arm with some risky running.
With runs hard to come by, they started to try the unorthodox and Niall O'Brien was the next to go when he reverse swept Hasan to backward point to leave Ireland 128-3 in the 34th over.
That brought his brother, Kevin O'Brien, to the crease and after playing himself in he injected some much-needed urgency.
It had been nearly 13 overs since the last boundary but he belted Razzak for a six and a four as 15 came off the 39th over.
Ireland lost the patient Porterfield with just over eight overs to go but O'Brien was determined to raise the run rate and he cracked 48, including two fours and two sixes, off 44 balls before becoming the third run out victim in the 48th over.
Captain Johnston also opened his shoulders, scoring 30 off 23 deliveries before falling in the final over, and they ensured Ireland posted a competitive total.
Kevin O'Brien scored quick runs late in the Ireland innings
Ireland's 6ft 8in opening bowler Boyd Rankin, who took 2-42, was always going to be handful on the bouncy track and he got Ireland off to a fine start when he forced Shahriar Nafees to glove a catch behind in the seventh over with the score on 18.
Aftab Ahmed, all 5ft 2in of him, briefly threatened, flicking the towering Rankin over mid-wicket for six, but he got carried away when Andre Botha was introduced into the attack.
The medium pacer served up a wide half-volley with his first delivery and Aftab provided Niall O'Brien with his second catch of the innings.
The Tigers then lost Hasan in unfortunate circumstances as he narrowly failed to recover his ground after Botha deflected a drive onto the stumps to leave them 48-3.
Bangladesh needed Ashraful and opener Tamim Iqbal to build a big partnership.
Both players duly unveiled some fine shots, with one text-book cover drive from Ashraful, the ball after he had pulled Botha for six, sending the knowledgeable Kensington Oval crowd into raptures.
But Tamim yorked himself for 29 when facing Trent Johnston and Ashraful soon pulled the same bowler straight down the throat of Dave Langford-Smith at deep square leg to leave Bangladesh 102-5.
Captain Habibul Bashar was given a massive let-off when Langford-Smith dropped him in a near carbon-copy of the Ashraful dismissal, Ireland kept the pressure on.
The Tigers edged their way to 131 but then lost three wickets for seven runs in just 18 deliveries.
Abdur Razzak provided some late resistance before he was cleaned up by off-spinner Kyle McCallan and Ireland captain Johnston wrapped things up when he bowled opposite number Bashar for 32.