Bill Browder spent a decade navigating the anarchic environment of post-Soviet Russia after moving to Moscow in 1996. He ran a hedge fund that would eventually become the largest outside investor in the country with more than $4.5 billion under management. 

The Stanford Business School graduate took a "naming-and-shaming approach" to his work, clashing with oligarchs and other Russian officials who he believed were taking advantage of the lawlessness of the "Wild East." 

"But, of course, exposing corrupt oligarchs didn’t make me very popular in Russia," Browder writes in his new book, "Freezing Order." "And, in time, my actions led to a cascade of disastrous consequences." 

Russian President Vladimir Putin blacklisted Browder in 2005, expelling him from Russia and sending his cronies to seize the assets of Browder's fund. 

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Browder evacuated his staff, liquidated the fund's holdings and hired a team of attorneys who would eventually accuse Interior Ministry officials of working with criminals to orchestrate a $230 million tax rebate fraud. 

One of those attorneys, Sergei Magnitsky, was arrested in November 2008 and spent nearly a year in a jail cell, where he was refused medical care for a host of issues he developed. On Nov. 16, 2009, Magnitsky was transferred to another detention center and beaten to death by a group of riot guards with rubber batons. 

In 2012, former President Obama signed the Magnitsky Act into law, which sanctioned the individuals believed to be responsible for the attorney's death and allowed the Treasury Department to target other human rights abusers in Russia. 

Browder has spent the years since then encouraging dozens of other countries around the world to adopt their own version of the Magnitsky Act, a mission that has taken on increased significance in the wake of Putin's invasion of Ukraine earlier this year. 

"This war is, for Putin, an existential war," Browder told Fox News Digital in an interview at the Texas Tribune Festival. 

"He started this war — not because of NATO or of some grand vision of Russian Empire — he started this war because he was afraid that someone was going to, or I should say, the people of Russia, were going to finally say enough is enough."

More than seven months into the invasion, Putin has failed to achieve his immediate goals, prompting the Kremlin to announce a "partial mobilization" last week and conscript 300,000 men into the military, a move that could backfire. 

"He's really walking a tightrope between having to be seen to be strong and upsetting a lot of people by drafting them, putting them in harm's way, having young men killed, in order to stay strong," Browder said. 

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The partial mobilization has met some resistance within Russia. 

More than 2,300 protesters have been arrested during demonstrations in dozens of cities. Some draft offices have been set on fire, while one 25-year-old Russian man opened fire at a miliary enlistment center in the Siberian town of Ust-Ilimsk, wounding the head of the office, according to Reuters. 

"You can be assured of one thing, which is that Putin always escalates. He has only a forward gear, no reverse gear. There's no possibility of negotiation. I've never seen him negotiate anything, so he's going to fight until he can no longer fight," Browder said. 

Putin recently threatened to use "all the means at our disposal" if Russia's "territorial integrity" is threatened, a statement that Ukrainian President Volodymyr Zelenskyy derided as "nuclear blackmail." 

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U.S. officials, meanwhile, have warned of "catastrophic" and "horrific" consequences for Russia if Putin did use nuclear weapons. 

"Putin is a psychopath. He holds nuclear weapons. He only cares about his own survival, and if he somehow saw the use of tactical nuclear weapons as a way of staying alive and staying in power, then he very well might," Browder said. 

The U.S. and Western allies have sent billions of dollars worth of military aid to Ukraine while slapping sanctions on Russian industry and oligarchs. 

Throwing a wrench in Russia's war machine won't be possible until the rest of the world joins in cutting off Russia though, according to Browder. 

"A lot of other countries — China, India, the United Arab Emirates, Turkey, South Africa, Brazil — are sitting it out, they're not involved in the sanctions," Browder said. 

"I think that we have to say to the countries that aren't participating, ‘You have a choice. You can either do business with the G7, which makes up the vast majority of the economic output of the world, or you can choose Russia.’"