The US just entered a great power arms race in a big way - and Russia and China are panicking

U.S. Army photo by Sgt. Michelle U. Blesam, 210th FA Bde PAO

An M270 multiple launch rocket system fires during a live fire exercise at Rocket Valley, South Korea, Sep. 15, 2017.

• The US tested its first post-INF Treaty missile, and it has Russia and China on edge, as both rivals are warning that the US is starting a new arms race that raises the possibility of armed conflict.
• On Sunday, the US tested its first ground-launched cruise missile since the Intermediate-Range Nuclear Forces (INF) Treaty collapsed earlier this month.
• Russia is warning that the US is setting "the course for fomenting military tensions," and China is expressing concerns that the US will "trigger a new round of an arms race."
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The US test of the country's first post-INF Treaty missile has Russia and China rattled, with each nuclear-armed rival warning that the US is igniting a great power arms race.

As Russia warned the US is setting "the course for fomenting military tensions," China expressed concerns that American actions will "trigger a new round of an arms race," making conflict more likely. Arms control experts have warned that a "new missile race" is underway, arguing that strategic rivals are likely to match US weapons developments "missile for missile."

The US military conducted its first flight test of a conventional ground-launched cruise missile on Sunday, firing off a missile that would have been banned under the Intermediate-Range Nuclear Forces (INF) Treaty a little over two weeks prior.

Read more: The US fired off a previously banned missile, the first since the collapse of a Cold War-era nuclear-arms pact with Russia

The 1987 INF Treaty was a Cold War-era agreement between Washington and Moscow that put restrictions on missile development, prohibiting either side from developing or fielding intermediate-range ground-launched missiles, systems with ranges between 500 km and 5,500 km. China, never a party to this pact, has been developing missiles in this range for decades.

Accusing Russia of violating the agreement through its work on the Novator 9M729, a missile which NATO refers to as SSC-8, the US warned earlier this year that it would "move forward with developing our own military response" to Russia's alleged violations of the accord, a position supported by NATO.

When the US formally withdrew from the treaty at the start of August, Secretary of Defense Mark Esper explained that the "Department of Defense will fully pursue the development of these ground-launched conventional missiles." Sixteen days later, the US tested its first post-INF missile - alarming not only Moscow, but also Beijing.

DoD photo by Scott Howe

On Aug. 18, at 2:30 p.m. Pacific Daylight Time, the Defense Department conducted a flight test of a conventionally configured ground-launched cruise missile at San Nicolas Island, Calif.

"We will not allow ourselves to get drawn into a costly arms race," Russia's Deputy Foreign Minister Sergei Ryabkov told Russian state media.

Urging the US to "let go of its Cold War mentality," Chinese Ministry of Foreign Affairs spokesman Geng Shuang stressed that the US test and future tests will ultimately lead to "an escalation of military confrontation, which will have a serious negative impact on the international and regional security situation."

Russia, which insists it did not violate the INF Treaty, has repeatedly warned the US against deploying intermediate-range missiles in Europe.

The weapon tested Sunday, as The War Zone explains, was a ground-launched BGM-109 Tomahawk, a variant of the BGM-109G Gryphon, one of the US missile systems that, together with the Pershing II mid-range ballistic missile, comprised the forward-deployed tactical nuclear forces in Europe before the INF Treaty was signed and all relevant weapon systems were destroyed.

In apparent response to Moscow, the US has said that it has no plans to put post-INF Treaty missiles in Europe. Beijing may actually have more reason to worry.

The Pentagon, specifically the new secretary of defense, has expressed an interest in positioning new intermediate-range missiles in the Pacific to counter regional threats like China. "Eighty percent plus of their inventory is intermediate-range systems," Esper told reporters during a recent visit to the region. It "shouldn't surprise [China] that we would want to have a like capability."

China did not respond positively to the news, warning that it won't let the US put missiles on its "doorstep." The US has yet to announce where any of these missiles will be deployed.

Read more: China warns it will not 'sit idly by' while the US moves to put new strike missiles on its 'doorstep'

While some observers see the US wading into a major arms race as it focuses more on great power competition, others see this as a reasonable strategic evolution in US military capabilities.

"We want China's leadership to wake up every morning and think this is not a good day to pick a fight with the United States or its allies," Tom Karako, a missile defense expert at the Center for Strategic and International Studies, told Insider.

Over the years, China has developed increasingly-capable missiles designed to target US bases across the Pacific, as well as sink US carriers at sea. The US has expressed interest in deploying new capabilities throughout the tilt the scales back the other way.