Military expenditures represent an important component of government spending devoted to the provision of national defense as a core public good. Despite their importance, no universally accepted definition of military expenditure exists, as national governments and international organizations apply differing conceptual and methodological approaches. This paper examines the evolution of defense burden, measured as military expenditure as a share of gross domestic product across NATO member countries from 2010 to 2025, with particular attention to NATO spending commitments adopted at the Wales Summit in 2014, all within the context of the current defense spending commitment adopted during the Hague Summit in 2025. Using SIPRI military expenditure data, defense burden trends are analyzed in three periods: pre-2014, post-2014 and pre-2022, and post-2022 following the full-scale Russian invasion of Ukraine. The results reveal a long-term shift from declining defense burdens prior to 2014 toward a sustained increase across most NATO members after the Wales Summit, with a pronounced acceleration after 2022. While the NATO-wide average defense burden rose above 2% of GDP by 2025, significant disparities among member states persist. A detailed case study of the Czech Republic demonstrates a broadly similar but lagging trajectory, with defense spending consistently remaining below NATO average and median values and failing to reach the 2% GDP threshold by 2025. The findings underscore structural differences in burden sharing within NATO and highlight the relevance of past spending behavior for assessing the credibility of current and future defense commitments.