• Ukraine has long been restricted from using Western missiles to strike inside Russia.
• The US relaxed some of the rules over the weekend following North Korea's involvement in the war.
• Kyiv has since used both ATACMS and Storm Shadow missiles to hit targets on Russian soil.

Ukraine is finally using its powerful, longer-range Western missiles to strike targets inside Russia after waiting over a year for permission.

On Wednesday, Ukraine fired British-made Storm Shadow cruise missiles at targets inside Russia for the first time, according to several media outlets and local footage. The UK defense ministry and Kyiv did not immediately comment on the reported developments.

Ukraine fired a volley of at least 10 Storm Shadow missiles into Russia, The Wall Street Journal reported, citing Ukrainian and Western officials.

The Storm Shadow strikes come a day after Ukraine first fired US-made tactical ballistic missiles, known as ATACMS, at a military facility in Russia's western Bryansk region. Kyiv acknowledged the strike but did not say what weapons were used.

Ukraine had long been prohibited from using these Western missiles to strike inside Russia, but President Joe Biden authorized the use of ATACMS over the weekend in a major policy shift, and the UK seemed to follow suit with Storm Shadow. Both missiles have now been used in strikes on Russian soil.

The removal of the restrictions on weapons usage follows the introduction of North Korean troops in the war — a development that NATO has called a "significant escalation" — and comes at a critical moment in the grinding conflict, which just passed the 1,000-day mark.

What are these missiles?

ATACMS, or Army Tactical Missile Systems, are short-range missiles made by US defense contractor Lockheed Martin. They can be fired from Ukraine's M142 High Mobility Artillery Rocket System or M270 Multiple Launch Rocket System, which are mobile ground-based launchers.

ATACMS can hit targets up to 190 miles away and, depending on the variant, carry unitary warheads or cluster munitions, which disperse little bomblets mid-flight over a large area.

The longest-range ATACMS variant has a farther reach than much of Ukraine's arsenal, including the British air-launched Storm Shadow cruise missile, which can strike targets around 155 miles away. It's unclear how many ATACMS and Storm Shadows Kyiv has available in its arsenal.

The Storm Shadow is made by the European multinational corporation MBDA. The missile has low-observable features, can carry a nearly 1,000-pound warhead, and fly at low altitudes to avoid detection. Like Britain, France has also provided Ukraine with its version of the weapon, known as SCALP-EG.

Ukraine debuted its ATACMS and Storm Shadow missiles last year but has been limited to using them against targets in territory that Russia illegally occupies in the eastern and southern regions, including the Crimean peninsula.

Ukrainian officials, including President Volodymyr Zelenskyy, have repeatedly lobbied for all restrictions to be dropped, and analysts have said the limitations have hamstrung Kyiv's ability to effectively defend itself. The US opposed the move, fearing it could escalate the conflict.

In the face of these restrictions, Ukraine has relied on domestically produced attack drones and missiles to carry out long-range strikes on sensitive military targets in Russia. This campaign has escalated in recent months.

However, the recent involvement of North Korea in the war appears to have moved the needle for the White House. Thousands of North Korean troops have been sent to Russia's Kursk region to help Moscow expel Ukrainian forces, who continue to hold a small chunk of territory there following a surprise invasion in early August.

Biden's policy shift comes just weeks before President-elect Donald Trump takes office. The incoming commander-in-chief is skeptical of US support for Ukraine and could decide to reverse the order.

The Kremlin has warned the West against allowing Ukraine to use its missiles to strike Russian territory. On Tuesday, President Vladimir Putin approved an update to the country's nuclear doctrine in a move that seemed to directly respond to the ATACMS policy reversal.