Birmingham signed Alexander Hleb from Barcelona and Martin Jiranek from Spartak Moscow on the final day of the transfer window.
Hleb, who has previously played in the Premier League with Arsenal, joined on a season-long loan deal from Spanish champion Barcelona. The Belrus midfielder spent last season on loan at Stuttgart.
Birmingham manager Alex McLeish says “Hleb is a top-quality player – one who at one stage we’d only actually dreamed about.”
Jiranek joined Thursday for an undisclosed fee on a one-year deal.