• Nato leaders fear the US may not come to their aid in case of a Russian attack.
• The Trump administration's rhetoric has created uncertainty about US commitment to European security.
• Eastern European countries are increasing defence spending and seeking alternative security arrangements.
• The US has announced a review of its force posture and basing in Europe.

The uncertainty surrounding US reliability may indicate a shift in the transatlantic alliance's dynamics, which could have significant implications for European security. The eastern European countries' efforts to increase defence spending and seek alternative security arrangements suggest they are preparing for a potential decrease in US commitment, which may lead to a more fragmented security landscape in the region.