Portugal flew out of the blocks in a battle of tournament debutants, with Jéssica Silva and Kika Nazareth both experiencing early sights of goal.
Francisco Neto’s side continued to flood forward with intent, and their first-ever goal at a WWC duly arrived in the seventh minute when Telma Encarnação guided the ball home from Lúcia Alves’s inviting delivery.
After creating the opener, Alves nearly had a goal of her own to celebrate, but she was unable to beat Trần Thị Kim Thanh in the Vietnamese goal.
However, there was nothing the goalkeeper could do to prevent Nazareth from calmly slotting home a second in the 21st minute after latching onto Encarnação’s neat pass to double the Selecção das Quinas’ lead.
With Vietnam at risk of capitulating in the first half, they would have been relieved to see Trần Thị make a couple of fine stops to deny Encarnação twice in quick succession.
Despite taking a two-goal lead into the interval, Portugal were in no mood to rest on their laurels in the second period.
A neat piece of skill from Silva created the space to stand the ball up to the back post for Encarnação, who was unable to keep her volley under the crossbar.
The woodwork then came to Vietnam’s aid when Joana Marchão’s scooped effort struck the crossbar before Trần Thị reacted quickly to thwart Nazareth from the subsequent rebound.
Marchão was made to rue her luck again in the final 10 minutes when she clipped the woodwork for a second time, leaving the European nation to settle for just the two goals.
Portugal will now turn their attention to a difficult meeting with the record champions the USA and will almost certainly need to pull off a shock win to advance to the Round of 16.
Vietnam, meanwhile, will wrap up their campaign against the 2019 runners-up the Netherlands.
