Travis Kalanick did not build Uber into a global force by playing nice.

Mr. Kalanick, the chief executive of Uber, a ride-hailing service, aggressively pushed the start-up into new markets, taking combative stances toward regulators and the powerful taxi industry — and the news media.

But Mr. Kalanick and his team have begun to trade the art of Sun Tzu for a full-throated charm offensive.

In January, Mr. Kalanick delivered a speech in Munich filled with talk about compromising with regulators he once sparred with, wanting to “make 2015 the year where we establish partnerships with new European cities.” The company also released two rosy, data-heavy reports about the service’s advantages on cities, drivers and communities. And on Friday, in an uncommon display of humility, Uber pledged to strengthen its user data privacy practices, acknowledging that “we haven’t always gotten it right.”

The striking reversal in tone comes at a crucial time for Uber, which once somewhat prided itself on its antagonistic attitude. The company is now valued by investors at over $40 billion after the most recent round of financing, largely on the promise of rapid growth. To build a business worthy of that valuation, though, the company must prove to investors that it can continue its breakneck pace of expansion in markets abroad at the same rate it has domestically.