BERLIN — German Chancellor Friedrich Merz urged Ukrainian President Volodymyr Zelenskyy to curb the flow of young Ukrainian men to Germany and ensure they stay to defend their country. “In a lengthy telephone conversation today, I asked the Ukrainian president to ensure that young men in particular from Ukraine do not come to Germany in large numbers — in increasing numbers — but that they serve their country,” Merz said Thursday. “They are needed there.” His comments come amid growing concerns