There are two distinct periods in Defense Institution Building in Ukraine since gaining independence in 1991. A period of peace until February 2014, and the period of war with Russia in 2014-2018. In the pre-war period of 1991-2013, the economic problems, inconsistencies in national strategy and consequent neglect of national defense requirements led to unclear military strategies and declarative rather than substantial reforms of the Armed Forces. Ukraine was trying to compensate the impact of its economic weakness and policy inconsistencies on defense through active cooperation with NATO and participation in peacekeeping operations under the auspices of the UN, NATO and the EU. However, in the spring of 2014, the response of Ukraine exposed serious weaknesses in all defense aspects except for the people’s will to defend the country. Responding to the Russian annexation of Crimea and the invasion to the South-Eastern Ukraine, Ukraine has mobilized, equipped, and trained a substantial military force of 250 000 active personnel and invested substantial resources in building effective military with agile professional active component supported by deployable ready reserve, jointly capable to deter possible aggression from Russia.