As tensions between the West and Russia grow over the Crimean dispute, a series of harsh sanctions is expected to be imposed on Russia in the coming weeks. While most of the focus is on Russian government officials, it is also said to include travel bans for the well-connected CEOs of OAO Gazprom (OTC:OGZPY) and OAO Rosneft.

Russian MPs aren't taking this lying down, and are threatening retaliatory sanctions against U.S. and European companies. The rest could well be a full-fledged sanction war, with tit-for-tat sanctions spiralling out of control.

Everyone loses in this war, but especially the Germans
While it's impossible to predict what form the retaliatory sanctions may take several steps down the road, even the backlash from the travel bans could be a nasty blow for some major European companies. Both Gazprom and Rosneft are hugely important to the economies of major European powers like Germany, and treating their CEOs as persona non grata is going to put a major strain on those ties.

The biggest and most immediate loser in all of this is E.ON (OTC:EONGY), the German utility giant. The company has carefully fostered close ties with Gazprom for years, and Germany is hugely dependent on Gazprom for natural gas. How big are these ties? Amid all of this sanctions talk, Gazprom CEO Alexei Miller was visiting Berlin to celebrate the anniversary of opening ties with E.ON. A travel ban could mean this is the last they'll be seeing of him for quite awhile.

That's bad news for E.ON, whose deep investment in those ties could rapidly evaporate amid a sanctions war. Gazprom is the largest natural gas producer in the world by far, and irreplaceable. The Russian gas giant is also making its first tentative steps into the Asia-Pacific market in recent months, and all this acrimony with the EU might convince the company Asia is simply a safer place to grow, leaving Europe figuratively and literally in the cold as their own gas demand grows.

With rising administrative costs and a mountain of debt already cutting into E.ON's profits, they weren't exactly high on the list of investments to begin with. With a Gazprom backlash hanging over their heads now as well, the stock should be avoided at all costs.

The Russian Arctic may be even less welcoming
Some European companies have been investing heavily in partnerships with Gazprom and Rosneft as well, with an eye on joint development of vast oil and gas fields in the Russian Arctic. Those deals are going to be tough to follow through on and may collapse outright as the sanctions war picks up.

BP plc (NYSE:BP) has invested billions into Rosneft, and owns almost 20% of the company now. If asset seizures start occurring back and forth, BP's investments are liable to be one of the earliest targets. This is doubly true because British Prime Minister David Cameron has been so gung-ho about the sanctions, going so far as to say he's willing to see damage done to London's economy so long as he can move against Russia.

On the Gazprom side of the equation, Royal Dutch Shell plc (NYSE:RDS.A) is a big investor in Russia's Pacific liquid natural gas export plant. While this plant might be taking on renewed importance with a Russian shift eastward, Shell might find itself a less inviting partner and watch its role in this potential growth market shrink. 

The bottom line
Neither BP nor Shell is facing a threat as near the immediacy or import as E.ON, whose very profitability might be at risk if things turn sour. BP's stock is a bargain on paper, with a P/E of around 6.5, though investors should keep a cautious eye on what happens with their Rosneft relations.

Shell's risk is even smaller, and it is well-positioned to take advantage of some other geopolitical situations, though with a price near its 52-week high, caution again is probably warranted, and panic selling on a sanctions war could provide a buying opportunity.

Gazprom remains the biggest bargain of the bunch, and even though it's the primary target of these sanctions, it is ironically in the least danger. Its gas empire is simply irreplaceable to the global economy, and with a P/E around 2 after the recent sell-off, it is just ridiculously cheap.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.