Though the Nord Stream 2 pipeline is a familiar term in European capitals, many Americans are hearing about it for the first time thanks to this week’s NATO summit. Throughout the event, President Trump picked at various scabs in German politics: that the Germans are overly reliant on Russian gas, that there’s an increasingly cozy relationship between Germany’s political elites and Russia’s Gazprom, that the country is a ‘captive of Russia,’ etc.

What is the Nord Stream 2 pipeline and why does it have the US president up in arms?