Germany shrugged off the absence of world number two Alexander Zverev to sweep past Slovakia in their Davis Cup group stage finals opener on Tuesday as Canada beat Argentina.
Despite the absence of their top four players, including Zverev, the Germans dominated their Group C tie 3-0 in Zhuhai, China.
The group also includes the United State and Chile.
Canada, the 2022 champions, eased past Argentina 2-1 in Group D action in Manchester, England.
Germany's Maximilian Marterer won the first point 6-4, 7-5 against Lukas Klein, with Yannick Hanfmann beating Josef Kovalik 3-6, 6-3, 7-6 (7/3).
Argentina hit back with Kevin Krawietz and Tim Puetz teaming up in the doubles to see off Klein and Igor Zelenay 7-5, 6-3.
The United States, 32-time champions, open their campaign against Chile on Wednesday, followed by Slovakia on Friday and Germany on Saturday.
"We have a few days off so we can recover and do our best to win the next matches and still have a chance to go to the final," said Slovakia's Jozef Kovalik.
In Manchester, Canada's Denis Shapovalov battled past Francisco Cerundolo 7-5, 6-3 in Group D before Felix Auger-Aliassime eased past Sebastian Baez 6-3, 6-3.
Maximo Gonzalez and Andres Molteni teamed up in the doubles to beat Shapovalov and Vasek Pospisil 2-6, 6-3, 6-2.
CANADA WIN! 🇨🇦
— Davis Cup (@DavisCup) September 10, 2024
The 2022 #DavisCup Champions get their campaign in Manchester off to a flying start with a 2-1 win over Argentina 🔥 pic.twitter.com/fRRYNvu4o0
Canada next play Finland on Thursday before taking on hosts Britain on Sunday.
"I feel great," said Shapovalov.
"The last time I played in the Davis Cup we won the competition, so it was nice to be back and playing at such a high level. I want to build on this now."
Champions Italy open their title defence on Wednesday in Bologna against Brazil but without world number one Jannik Sinner, winner of the US Open at the weekend.
Italy are in the same Group A as Belgium, who bounced back from going 1-0 down to defeat the Netherlands 2-1.
In their first meeting since 1998, where the Netherlands came out on top, Belgium now gets their revenge with a victory over the Dutch 👊🇧🇪#DavisCup pic.twitter.com/NSIlIWqd2D
— Davis Cup (@DavisCup) September 10, 2024
In Group B, 10-time winners France lost 2-1 to Australia, losing finalists in 2022 and 2023.
Playing in Valencia, Australia took the lead after Thanasi Kokkinakis beat Arthur Fils 7-6 (7/4), 7-6 (7/3).
Ugo Humbert levelled for the French, the France number one downing Alexei Popyrin 6-3, 6-2.
The Aussies took the tie when Matthew Ebden and Max Purcell (AUS) saw off Edouard Roger-Vasselin and Pierre-Hugues Herbert 7-5, 5-7, 6-3.
Carlos Alcaraz's Spain are also in Group B.
The top two nations in each of the four groups in the round robin competition will qualify for the eight-team final in Malaga, Spain from 19-24 November.