The Open Skies Treaty was meant to improve trust between Russia and the West by allowing the accord's three-dozen-plus signatories to send reconnaissance flights over each other's territories and collect intelligence on military forces and activity.
In a classified State Department memo obtained by Newsweek, Secretary of State Mike Pompeo suggested Russia may been capturing images of infrastructure for the purposes of targeting it with "conventionally-armed, precision-guided weapons."
Rep. Eliot Engel, the chairman of the House Committee on Foreign Affairs, wrote to National Security Advisor Robert O'Brien Monday to request clarification on the reports.
Suddenly, Cold War nuclear threats the treaty had long defused are coming back.
President Donald Trump said the U.S. "will work with NATO and our other allies and partners to deny Russia any military advantage from its unlawful conduct."
Trump is tearing up an actually functioning treaty that has reduced the threat of global nuclear war. His record on North Korea does not bode well for whatever he is hoping to put in its place.
Russia's deputy foreign minister said that "there are less and less people in Washington now who are ready to consider arms control as an effective way of ensuring their own security."
Russian Foreign Minister Sergey Lavrov said that "there is no doubt that there can be no winners in a nuclear war and it should never be unleashed."
"We will find ourselves at ground zero," Russian Senator Alexei Pushkov warned.
"It is time now for Russia to come to the table and stop the violations," the U.S. ambassador to NATO told reporters.
With no official peace treaty and a heavily fortified border between them, the Koreas are still very much living the Cold War.
Foreign Minister Sergey Lavrov said the treaty "triggers strong differences between the members of the international communities."
Thirty years after Gorbachev and Reagan signed a landmark deal to stop an arms race in Europe, the pact was on the fritz.
Article 29 of the Iran nuclear deal states that no country should discourage trade with Iran, something President Donald Trump has done for some time.
Former U.S. and Israeli generals disavow a possible U.S. military strike on Iran, and a European scholar says Trump may find himself isolated.
Ronald Reagan and Mikhail Gorbachev signed the Intermediate-Range Nuclear Forces Treaty in 1987. Now Republican hawks want to scrap it.
Withdrawal from the treaty will do nothing to hurt the environment, and may help it.
European integration was an outcome of America's rebuilding of Europe after World War II.
Given Putin's efforts to woo EU states such as Italy, France and Greece, the U.K.'s departure could tip the balance on sanctions against Russia.
Whoever is elected president will confront one of the most profound tasks of any post-war U.S. president: reimagining a threatened world order.
Voters feel trapped between supporting EU bureaucrats or strengthening Putin's hand.