Australia set England an unlikely 383 runs and just more than a day to win or save the test, and Cummins undermined the home team's hopes by dismissing Rory Burns and captain Joe Root for ducks in the first over.
Jason Roy defended Cummins' hat trick ball, and from 0-2 after only four deliveries, England reached stumps on 18-2 from seven overs. With the five-match series at 1-1, Australia can retain the Ashes with victory at Old Trafford. That's more likely than England surviving a fifth-day pitch against an Australia team full of self-belief. The forecast is for a dry Sunday.
"We know that the bail height is going to be the hardest to play, so it's about trying to hit the stumps as much as we can," Cummins said. "One big final push tomorrow." After England's first innings was ended on 301, conceding a lead of 196, Smith and Matthew Wade revived Australia from 44-4 in their second innings with a stand of 105.
With uncharacteristic haste to give his side the chance to declare, Smith made 82 from just 92 balls, and yet his lowest score in this series after a double century, two centuries, and a 92. "None of us really expected the innings that Smithy went out there with. He was incredible," Cummins said.
"We would have been happy just to get through the night and have a good score for tomorrow morning but Smithy was unbelievable out there." Wade added 34, and captain Tim Paine had the luxury of declaring their second innings on 186-6 in the middle of the 43rd over, and a lead of 382. On 23 not out at the time, Paine sprinted off the Old Trafford field so he could give his bowlers seven overs to attack England in evening light.
Cummins' double strike in two balls exceeded expectations. Burns, trying to work the ball to the leg side, popped the ball to short cover. Root came out and a length ball zipped past his defense and took out his bails.
Root was almost disbelieving, as he became the first England captain to make three ducks in a test series. England also started the day batting, resuming its first innings on 200-5, avoiding the follow-on after lunch and finishing all out for 301.
Mitchell Starc took three wickets, his first in this series, and fellow fast bowler Cummins took the others, including last-man Jos Buttler on 41, to give him 3-60. Australia, with a lead of 196, faltered badly.
Opener David Warner completed a match pair of ducks when he was trapped leg before wicket by Stuart Broad, also before Australia scored. Broad also got Warner in the first innings, and for the sixth time in eight innings in this series.
Broad also took out the other opener, Marcus Harris, and Jofra Archer bagged Marnus Labuschagne and Travis Head to reduce Australia to 44-4 and a lead of 240. But Smith counterattacked with some unorthodox strokes in hitting a one-day-like 11 boundaries, some of them while he was falling backwards.
Root seemed to let Smith and Wade hit away after tea, until Smith, who appeared set for another century, skied Jack Leach and was caught at long off. Wade fell in the next over but Australia was back in charge, and Cummins underlined it with the ball.
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