Investors appeared unconvinced. Deutsche Bank shares opened higher in trading in Frankfurt, but then gave up the gains and were down around 6 percent at the market’s close.

Many elements of the bank’s turnaround plan will take months or even years to put in place, including an effort to sequester high-risk assets in a separate unit where they will be sold or retired.

But cutting jobs can be done quickly, at least in countries like the United States and Britain, where there are few legal obstacles. So employees felt the most immediate impact of the bank’s plan to reverse its fortunes, leading to scenes outside Deutsche Bank offices that recalled those that unfolded during the financial-sector layoffs after the investment bank Lehman Brothers collapsed in 2008.

Although Mr. Sewing declined on Monday to detail how the cuts, which will ultimately total 18,000 worldwide, would be distributed, they are most likely to be concentrated in New York and London, and in places, like Singapore, where Deutsche Bank has large investment-banking operations.

Layoff announcements were made to at least two groups at the bank’s United States headquarters in Lower Manhattan. Employees on their way into the building described an office that had been dominated by a sense of foreboding. Around 10 a.m., a group of employees emerged carrying white envelopes containing information about the dismissals. One woman appeared to be crying.