It was a bold move to declare after 78 overs of a first innings, the earliest any team has ever declared in an Ashes series, but it's not out of character for this team. That is now five first innings declarations from England in 14 tests.
A thrilling opening day, however, belonged to Root, who, as all eyes were on England's free-scoring batters to see whether they would stick with their attacking principles, proved his more reserved approach is still as effective as "Bazball".
"Once Joe had got his 100, there were quite a few shots being played, so we sort of sensed it (the declaration) was coming," Australia's Josh Hazlewood said.
"That's just the way they are playing cricket at the moment. We are still pretty happy."
ROOT'S BAZBALL INTERPRETATION
Many experts predicted in-form England, who had scored at almost five runs per over in 11 test wins from 13 under Brendon McCullum and skipper Ben Stokes, would struggle to still score freely in an Ashes series against such a strong Australian bowling attack.
But such doubts were quickly put to bed as Zak Crawley hammered a boundary off the first ball of the innings. It was in stark contrast to the first ball of the last Ashes series, when Mitchell Starc clean bowled England opener Rory Burns, ahead of Australia's rampant 4-0 success.
Root joined Crawley at the crease after the dismissals of Ben Duckett and Ollie Pope. Duckett (12) flat-footedly cut at a wide delivery from Hazlewood and got a thin low edge to wicketkeeper Alex Carey, while off-spinner Nathan Lyon dismissed the latter LBW.
Crawley reached his 50 off just 56 balls, only to get a glove on what was the final delivery before lunch after a beauty from Scott Boland.
His sparkling innings - including six fours -- was a reward for the faith shown in the talented but inconsistent opener by captain Ben Stokes and McCullum.
Harry Brook, who has been at the forefront of this new attacking approach for England having scored four centuries in seven test matches prior to the start of the Ashes, raced onto 32 off 37 balls before a blocked shot looped back over his head and onto the stumps in freakish fashion.
Stokes's demise was all his own doing, however, as Hazlewood, who impressed with the ball on what was his fourth international test appearance in two and a half years, found the captain’s edge with only one run on the scoreboard.
Root, who was given out just before tea only for the Decision Review System to come to his rescue, carried on ticking along as other teammates came and went.
As has been the case for many years, Root steadied the ship, putting together a partnership of 121 with fellow Yorkshireman Jonny Bairstow, who eventually fell for 78, to save his country in the hour of need again.
There were elements of the required aggression under McCullum, with four of the hosts' five sixes in the innings coming from Root's bat.
A flick off the legs for a single was all that was needed to see him over the line for that 30th international career century, before the shackles really came off, with two sixes in one over persuading Stokes to put Australia in earlier than everyone in attendance expected.
While there were a few shouts from a crowd spoiled for excitement overall, Warner and Khawaja looked comfortable to set things up for day two nicely.
See the scorecard from the first day of the first Ashes test on Flashscore