By announcing that it would deploy fighter planes to Ukraine, Poland defies its NATO partners.

Poland has pledged to send four MiG-29 fighter jets to Ukraine, the first NATO member to do so, in a significant move in Kyiv's battle to resist Russia's onslaught. President Andrzej Duda said the planes would be handed over in the coming days after being serviced. The announcement marks a break from the alliance, and could put pressure on other member states to do the same. Poland had been one of the most vocal European nations against Russia before the invasion of Ukraine, and is one of the few NATO countries that by law is required to meet its 2% of GDP defense spending commitment. Sending MiGs is not an unexpected move and complies entirely with Poland's membership of NATO.

The White House said Thursday that Poland's decision to send fighter jets to Ukraine is a "sovereign decision" that won't spur President Joe Biden to send F-16 aircraft. US and European officials have previously told CNN that F-16 fighter jets were impractical in this situation. German Chancellor Olaf Scholz announced his country would provide 14 Leopard 2 tanks in January, bowing to international pressure. The US also announced that it would provide 31 M1 Abrams tanks to Ukraine, reversing the administration's longstanding resistance to requests from Kyiv for the highly sophisticated but maintenance-heavy vehicles. Ukraine has also been pushing for the US to provide fighter jets, arguing that it needs the planes to defend against Russian missile and drone attacks. However, US and allied officials have said the jets would be impractical because they require considerable training and Russia has extensive anti-aircraft systems that could easily shoot them down.