World fuel prices jumped and stock values fell as Russian forces invaded its neighbor Ukraine on Thursday morning. But few big U.S. companies have as much at stake as EPAM Systems Inc., a Newtown, Bucks County-based software company with technical staff across the former Soviet Union.

EPAM employs more than 40,000 worldwide. That includes 13,000 in Ukraine, EPAM’s chief executive, Arkady Dobkin, told investors last week. EPAM has engineers and other professionals based in a dozen Ukrainian cities, including Kyiv, the capital, and Kharkiv, among the cities bombed by Russian forces.

Shares of EPAM opened down 16% Thursday morning, at $350, as images of Russian forces bombing Ukraine airports and cities flashed around the world. But the stock recovered somewhat by day’s end, closing down 8.6%, or $35.95, to $382.28.

Dobkin started the company in 1993, four years after the Berlin Wall fell, and built it into a $1 billion-plus (yearly sales) multinational business by hiring engineers in former Soviet republics to write and update software for bargain-hunting Western companies. Dobkin also grew the company through a string of acquisitions.

The company’s stock had soared last year as EPAM was added to the S&P 500 index, putting it into the retirement portfolios of millions of U.S. investors. But EPAM has lost almost half its value since December on fears of war and likely Western sanctions against Russia and its ally, Belarus, which on Thursday served as a base for attacks on Ukraine.

EPAM also employs local staff in several Russian and Belarusan cities, in Ukraine’s Western-aligned neighbors Poland and Bulgaria, and in the three Baltic republics, Estonia, Latvia, and Lithuania, U.S allies that border Russian-controlled territory and are watching Russia’s attack on Ukraine with alarm. More than 20 Pennsylvania National Guard soldiers and airmen are scheduled to be in Lithuania next week to conduct training, said spokesman Capt. Travis Mueller, who is based in Fort Indiantown Gap.

Just last Thursday, Dobkin, who was born in Belarus, had downplayed the impact of what he considered Russia’s likely actions against Ukraine at his company’s quarterly conference call with investors.

Asked by analyst Ramsey El-Assal of Barclays investment bank whether EPAM’s work would be disrupted by a Russian attack, Dobkin said there was relatively little disruption when Russia seized parts of Ukraine along that country’s eastern and southern borders in 2014, and he expected a similar result this time.

He noted that EPAM staff now typically works at home and isn’t dependent on local telecom infrastructure. Even if systems are wrecked or disrupted, the work can resume from other locations.

Some EPAM clients were very worried about the prospect of war in Ukraine, but a majority were not, Dobkin claimed.

The company has sought to become less reliant on Ukraine and its neighbors, especially in the last year, Bryan Bergin, a stock analyst at Cowan Inc., noted during the investor meeting.

Dobkin said EPAM has been expanding most rapidly in Latin America and India, but acknowledged that Russia, Ukraine and Belarus still account for more than half the company’s production.

EPAM has not made a statement about the Russian attack since it began. Company officials didn’t return calls seeking comment on Thursday.