text: Both sides had one defeat and a draw from the opening two league matches but Arsenal's impressive first-half performance earned them three points.
  A Santi Cazorla penalty, Alexis Sanchez's fumbled effort and Mesut Ozil's header gave the Gunners a 3-0 lead at half-time.
  Substitute Roberto Pereyra scored for the Hornets on his debut but it proved to be a consolation for the hosts.
  Walter Mazzarri's side put in a much-improved performance after the break but the Italian was made to wait for his first win as Watford manager.
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  Much like in previous seasons, Arsenal boss Arsene Wenger has been under pressure from some Gunners fans to spend money in the transfer market.
  It was revealed on Friday that Germany defender Shkodran Mustafi and Spanish striker Lucas Perez were undergoing medicals at the Emirates, and Wenger confirmed after Saturday's win that the deals were done, which takes the club's spending to almost £100m since last season.
  But they did not look like a team in need of extra artillery after a polished first-half display against Watford.
  The Gunners broke the deadlock when Sanchez was knocked on the head in the area by Nordin Amrabat, and Cazorla slotted the resulting penalty down the middle.
  Sanchez, who looked lively throughout, made it 2-0 when he scrambled home from an accurate Theo Walcott ball into the box.
  And Germany forward Mesut Ozil, making his first start for Arsenal after being rested post-Euro 2016, looked to have put the result beyond doubt on the stroke of half-time when he headed in from Sanchez's pass.
  Mazzarri, who arrived in the summer, has spent the last two weeks reinforcing his team, bringing in forward Roberto Pereyra from Juventus, Younes Kaboul from Sunderland and fellow defender Daryl Janmaat from Newcastle.
  The Hornets boss described Pereyra as the "missing point" of his squad and the introduction of the 25-year-old from Argentina invigorated Watford's performance in the second half.
  His goal came after Etienne Capoue's fierce strike was blocked, and Pereyra pounced and finished with his left foot.
  Arsenal keeper Petr Cech was then forced into action to save Jose Holebas' thunderbolt and he also had to react quickly to Odion Ighalo's follow up.
  Although it was a spirited recovery, the damage was already done in the first half.
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  Watford manager Walter Mazzarri: "The second half we were good and should have scored more.
  "Cech played incredible for them, saved a goal two or three times but I am very happy with how our team played.
  "A lot of players are new so we have to prepare later. The organisational things are still missing and two starting players were out last minute and this really didn't help."
  Arsenal manager Arsene Wenger: "We had a good cushion at half-time. At the moment we are not completely there physically and could see that in the second half.
  "Ozil is not physically there completely but what we want from Ozil is assists and goals and I hope he can get that this season, 10 or 15 goals plus the chances he creates.
  "We have bought two players - Mustafi and Perez. They will integrate into the team now and we will help them join the squad. We had to work very hard to get signings done. We have not got any plans for anyone else now."
  After the international break, Watford travel to West Ham on Saturday, 10 September while Arsenal host Southampton.
  Match ends, Watford 1, Arsenal 3.
  Second Half ends, Watford 1, Arsenal 3.
  Jack Wilshere (Arsenal) wins a free kick on the left wing.
  Foul by Valon Behrami (Watford).
  Attempt missed. Troy Deeney (Watford) header from the centre of the box is too high. Assisted by Isaac Success with a cross.
  Jack Wilshere (Arsenal) is shown the yellow card for a bad foul.
  Foul by Jack Wilshere (Arsenal).
  Etienne Capoue (Watford) wins a free kick on the left wing.
  Alexis Sánchez (Arsenal) wins a free kick in the defensive half.
  Foul by Sebastian Prödl (Watford).
  José Holebas (Watford) is shown the yellow card for a bad foul.
  Jack Wilshere (Arsenal) wins a free kick on the right wing.
  Foul by José Holebas (Watford).
  Mohamed Elneny (Arsenal) wins a free kick in the attacking half.
  Foul by Etienne Capoue (Watford).
  Foul by Jack Wilshere (Arsenal).
  José Holebas (Watford) wins a free kick in the defensive half.
  Attempt saved. Alexis Sánchez (Arsenal) right footed shot from outside the box is saved in the top right corner.
  Mohamed Elneny (Arsenal) wins a free kick in the defensive half.
  Foul by Roberto Pereyra (Watford).
  Foul by Héctor Bellerín (Arsenal).
  Etienne Capoue (Watford) wins a free kick in the defensive half.
  Valon Behrami (Watford) is shown the yellow card for a bad foul.
  Theo Walcott (Arsenal) wins a free kick in the defensive half.
  Foul by Valon Behrami (Watford).
  Attempt missed. Valon Behrami (Watford) right footed shot from outside the box misses to the left. Assisted by Roberto Pereyra.
  Corner,  Arsenal. Conceded by Isaac Success.
  Attempt saved. Odion Ighalo (Watford) left footed shot from outside the box is saved in the bottom right corner.
  Attempt saved. Isaac Success (Watford) header from the centre of the box is saved in the centre of the goal. Assisted by Etienne Capoue with a cross.
  Corner,  Watford. Conceded by Rob Holding.
  Foul by Santiago Cazorla (Arsenal).
  Etienne Capoue (Watford) wins a free kick in the defensive half.
  Substitution, Watford. Isaac Success replaces Nordin Amrabat.
  Nordin Amrabat (Watford) is shown the yellow card for a bad foul.
  Jack Wilshere (Arsenal) wins a free kick in the defensive half.
  Foul by Nordin Amrabat (Watford).
  Foul by Alexis Sánchez (Arsenal).
  Valon Behrami (Watford) wins a free kick in the defensive half.
  Substitution, Arsenal. Kieran Gibbs replaces Nacho Monreal because of an injury.
  Delay over. They are ready to continue.
target: Arsenal beat Watford to earn their first victory of the season.