When a Russian destroyer sailed 50 to 100 feet from a U.S. Navy guided-missile cruiser on Friday -- a distance so close the American ship had to make last-second maneuvers to avoid a collision -- it was just the latest in a series of close calls between the U.S. and Russian militaries.
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The USS Chancellorsville was operating in the Philippine Sea at approximately 11:45 a.m. on Friday when the Russian ship "maneuvered from behind and to the right of the Chancellorsville, accelerated, and closed to an unsafe distance" of between 50 and 100 feet, the U.S. Navy's Seventh Fleet said in a statement.
"This unsafe action forced Chancellorsville to execute all engines back full and to maneuver to avoid collision," the statement continued.
The U.S. Navy characterized the Russian ship's actions as "unsafe" -- the term typically used by the U.S. military to describe risky close calls experienced by its ships and aircraft in international waters and airspace.
With American military ships and planes conducting regular operations worldwide, there is always a chance for close encounters with the Russian military, which also operates globally.
How often do those types of unsafe interactions occur?
Not often, but when they do, they gain a lot of attention. If the incidents are deemed dangerous enough, the U.S. will file a formal diplomatic complaint with Moscow, called a démarche, but in the end, all that usually happens is that the U.S. military issues statements reaffirming its right to sail or fly through international waters and airspace.
On Friday, Acting Defense Secretary Patrick Shanahan reacted to Friday's incident between the Russian destroyer and the Chancellorsville, telling reporters the U.S. would have military-to-military conversations with the Russians and "démarche them."
"But you know it's -- to me, safety at the end of the day is most important. It will not deter us from conducting our operations," he said.
U.S. officials believe Russia's close encounters with the U.S. military are prompted by Russia's effort to reassert itself militarily around its borders.
In recent years, the closest encounters have been in the Baltic Sea and the Black Sea, involving Russian military aircraft buzzing American ships and flying too close to American planes.
Earlier this week, a U.S. P-8A Poseidon reconnaissance aircraft experienced an "unsafe" and "irresponsible" intercept by a Russian fighter over international waters above the Mediterranean Sea.
In late May, U.S. Air Force F-22 fighters intercepted Russian aircraft that had entered the Alaska Air Defense Identification Zone (ADIZ) for the second day in a row.
Russia isn't the only nation with which the U.S. military has had these close encounters.
In October, there was a particularly notable incident between the USS Decatur and a Chinese warship in the South China Sea. The Chinese ship sailed within 135 feet of the Decatur's bow, similarly prompting the American ship to take evasive maneuvers to avoid collision.