* Josef Ackermann to step down from Siemens board
* Retreat follows boardroom battle over CEO succession
* Ackermann was second deputy chairman at Siemens
BERLIN, Sept 12 (Reuters) - Former Deutsche Bank Chief Executive Josef Ackermann said he would step down from thesupervisory board of German engineering conglomerate Siemens, marking another retreat for one of Europe's mostpowerful executives.
His resignation as second deputy chairman at Siemens comesjust two weeks after the Swiss national quit as chairman ofZurich Insurance, following the suicide of the chieffinancial officer.
"I have decided to step down from the supervisory board ofSiemens. I will however retain all my other board seats." hetold reporters in Berlin on Thursday.
He is also a non-executive director at Royal Dutch Shell, a director at Investor AB, the investment companyfounded by Sweden's Wallenberg family, and a member of the boardof directors at private equity firm EQT.
In June, Ackermann clashed with fellow Siemens directorsduring a tussle over whether to oust Chief Executive PeterLoescher.
When supervisory board chairman Gerhard Cromme pushed forLoescher to be removed immediately, Ackermann was among the fewexecutives on the board to dissent. Siemens named finance chiefJoe Kaeser to replace Loescher soon thereafter.