Borussia Dortmund have signed Lukasz Piszczek and Mitchell Langerak, while Robert Lewandowski is on the verge of joining the Bundesliga side.
Right-winger Piszczek has signed a three-year contract and arrives on a free transfer from Hertha Berlin after the Poland international's contract was terminated following their relegation to the second division.
Australian goalkeeper Langerak has arrived from Melbourne Victory and will fill the void left by the transfer of Marc Ziegler to Stuttgart, providing back-up to number one Roman Weidenfeller.
"I have heard a great deal about the history and the successes of Borussia Dortmund," the 21-year-old shot-stopper told the club's official website.
"I also know that Roman Weidenfeller is a fantastic goalkeeper and I would like to learn a lot from him."
Dortmund are also reportedly close to increasing the Polish contingent at the club even further after Lewandowski was spotted arriving at the club's headquarters on Wednesday.
The 21-year-old striker, who scored 18 goals for Lech Poznan last season, has reportedly agreed terms with the Westphalian club, who are now in negotiations with Poznan over a transfer fee.