The Independent state of Croatia was established in parts of occupied Yugoslavia on 10 April 1941, after the invasion by the Axis powers. Its territory consisted of most of modern-day Croatia and Bosnia and Herzegovina, as well as some parts of modern-day Serbia and Slovenia, but also excluded many Croat-populated areas in Dalmatia (until late 1943), Istria, and Međimurje regions (which today are part of Croatia).
Michel 1 to 8 "Overprinted Yugoslavian Stamps"
Issued 12th Apr 1941. Yugoslavian issued stamps with black overprint 'NEZAVISNA / DRŽAVA / HRVATSKA / IIIIII', printed typography on unwatermarked paper and perf 12½.