At the Wales Summit in 2014, in response to Russia's illegal annexation of Crimea, and amid broader instability in the Middle East, NATO Leaders agreed a Defence Investment Pledge to reverse the trend of declining defence budgets and decided:
Allies currently meeting the 2% guideline on defence spending will aim to continue to do so;
Allies whose current proportion of GDP spent on defence is below this level will: halt any decline; aim to increase defence expenditure in real terms as GDP grows; and aim to move towards the 2% guideline within a decade with a view to meeting their NATO Capability Targets and filling NATO's capability shortfalls.
https://www.nato.int/cps/uk/natohq/topics_67655.htm?selectedLocale=en