BERLIN — German police on Wednesday arrested five teenagers accused of involvement with a right-wing extremist group calling itself “Last Defense Wave” that allegedly aimed to destabilize the country’s democratic system by carrying out attacks on migrants and political opponents. The early-morning arrests in various parts of Germany were accompanied by searches at 13 properties, federal prosecutors said in a statement. Four of those arrested — identified only as Benjamin H., Ben-Maxim H., Lenny M. and Jason R., in line with German privacy rules — are suspected of membership in a domestic terror organization. The fifth, Jerome M., is accused...