As Secretary of State Mike Pompeo prepares to meet President Volodymyr Zelensky of Ukraine in Kyiv later this week, he has reportedly asked, “Do Americans care about Ukraine?”

Here’s why the answer should be yes: Ukraine is defending itself and the West against Russian attack. If Ukraine succeeds, we succeed. The relationship between the United States and Ukraine is key to our national security, and Americans should care about Ukraine.

Russia is fighting a hybrid war against Ukraine, Europe and the United States. This war has many components: armed military aggression, energy supply, cyber attacks, disinformation and election interference. On each of these battlegrounds, Ukraine is the front line.

For the last seven months, I represented the United States in Ukraine and regularly visited the front line of the military conflict. After its occupation of Crimea, Russia sent its army, security forces, undercover agents, weapons, funding and political instruction into Ukraine’s southeastern provinces of Donetsk and Luhansk, a region known as the Donbas. The 280-mile line of contact between Russian-led forces and Ukrainian forces has stabilized but has not gone quiet.

To the contrary, the front line in the Donbas region marks the only shooting war in Europe. Every week Russian-led forces kill Ukrainian soldiers — and take casualties in return. During the 12 hours of my last visit, in November, a Ukrainian soldier was killed and another wounded. Since the Russians invaded in 2014, 14,000 Ukrainians have died in this war.

The United States and our allies support Ukraine in this war by providing the Ukrainian armed forces with weapons, training and support. American security assistance to Ukraine regularly receives broad, bipartisan support in Congress; the importance of that assistance to Ukraine — and to U.S. national security — is not at issue.

On the energy battlefield, the Kremlin is trying to bypass Ukraine and increase German and European dependence on Russia by spending billions on an unnecessary underwater natural gas pipeline, a political project without economic justification. In another show of bipartisan political support for Ukraine, Congress late last year passed sanctions on companies attempting to complete the pipeline, forcing a significant delay in the project.

Russia’s hybrid war is also an information war. Starting at home, Russian media is dominated by the state, leading its citizens to believe they are under threat from a hostile West and convincing them that President Vladimir Putin protects them from corrupt enemies. Russia’s trolls and internet hackers target Ukrainian, European and American political and social fault lines, exaggerating differences and fomenting dissension. They seek to weaken Western alliances, undermine confidence in democratic institutions, and turn citizens against citizens. We and other NATO allies are working with Ukraine to counter this malign influence.

The Russians interfered in our elections in 2016 — but not before interfering in Ukraine’s elections in 2014, and Britain’s Brexit referendum earlier in 2016. Because Ukraine is the front line, we assisted the Ukrainian central election commission in its preparations for their 2019 elections to defend against further Russian interference. Their efforts, with our assistance, successfully frustrated Russian attacks.

But the Russian challenge is even broader than hybrid warfare. The Kremlin is attacking the rules that have guided relations among nations since World War II, rules that kept the peace among major European powers for 70 years. With their invasion of Ukraine in 2014, Mr. Putin trashed those rules, spurned international consensus, violated the treaties and principles that even previous Russian and Soviet leaders had respected — even in the breach.

Mr. Putin seems to want to return to the law of the jungle that characterized relations among nations for centuries before 1945, where powerful nations dominated and invaded less powerful nations, where nations established spheres of influence that oppressed neighbors, leading to war and suffering. That was how the Russian Empire and Soviet Union conducted international relations — dominate, control and absorb neighboring lands. A return to jungle rules threatens not just Ukraine and the United States, but global stability itself.

Until Russia withdraws from Ukraine — both Donbas and Crimea — and recognizes that Ukraine is an independent, sovereign nation, other nations cannot be secure. Until Russia recommits to a rules-based international order, Western nations are in jeopardy. Ukraine is the front line.

In an even broader sense, Russia’s attack on Ukraine and the West is an attack on democracy. The question of how nations govern themselves — democracy versus autocracy — is being fought out among and within nations. Russia, China, Iran, Egypt, Turkey, the Philippines, North Korea, Venezuela, Cuba, Syria — all are autocracies, all are unfree. In the contest between democracies and autocracies, the contest between freedom and unfreedom, Ukraine is the front line.

To support Ukraine means to support a young democracy, fighting to regain sovereignty over its internationally recognized borders. It is to support a nation that has broken from its troubled past to embrace European and Western values and that seeks to join European and North Atlantic institutions, to defeat post-Soviet corruption, and to give its citizens the chance to prosper in a normal country.

To support Ukraine is to support a rules-based international order that enabled major powers in Europe to avoid war for seven decades. It is to support democracy over autocracy. It is to support freedom over unfreedom. Most Americans do.