Deutsche Bank laid off staff from Sydney to New York as it began to slash 18,000 jobs in a €7.4 billion "reinvention" that will lead to yet another annual loss.
The plan knocked its already battered shares on Monday.
Germany's largest lender said over the weekend that it would scrap its global equities unit and cut some fixed-income operations in a retreat from a long-held ambition to make its struggling investment bank, with 38,000 staff, a force on Wall Street.
Deutsche Bank has almost 91,500 staff around the world.
Its shares erased early gains and closed down 5.4% in Frankfurt after its finance chief flagged "significant uncertainty" over breaking even in 2020.
Its bonds also fell.
US-listed shares dropped 6.1%.
Some analysts were sceptical that the bank could grow future earnings quickly enough to reach a new target to achieve a return on tangible equity of 8% by 2022, compared with a negative return last year.
Ratings agency Fitch said that the bank's future credit rating will depend on how successfully it executes the plan.
Fitch downgraded the bank to "BBB" status, the lowest investment-grade status, just last month.
"The restructuring measures involve large staff cuts and significant leadership changes, which could disrupt the aim to improve core earnings," it said in a note published Monday.
Rating agency Moody's said there were "significant challenges" to executing the plan swiftly, adding it would keep its negative outlook.
The bank said on Sunday that it would not need to raise capital to initiate the cuts, which will result in it making a loss of €2.8 billion in the second quarter.
It will not pay a dividend either this year or next.
Deutsche Bank had been one of the few European banks to maintain a significant presence in the United States after the 2007-2009 financial crisis.
However, it has struggled to compete with US rivals, hampered by regulatory investigations and litigation.
The United States had been seen as a likely focus of the cuts although the bank maintained it wants to keep a significant presence, in part to service European corporate clients doing business in the country.
However, some shareholders have pushed for a full US retreat.
Deutsche Bank said it remained committed to the United States, its second-biggest market.
In London, where hundreds of job cuts were expected, Chief Executive Officer Christian Sewing said he was "reinventing" the bank, which is expected to post a loss this year.
That would put it in the red for four of the past five years after a series of damaging setbacks.
As part of the overhaul, Deutsche Bank will set up a so-called "bad bank" to wind down unwanted assets, with €74 billion euros of risk-weighted assets.
Deutsche Bank did not give details on the job cuts, but said they would be spread around the globe, including in Germany.
In Sydney, Hong Kong and elsewhere in the Asia-Pacific region, where Deutsche Bank used to rank among the top 10 in league tables for equity capital market (ECM) deals, several bankers said entire teams in sales and trading were going.