Wanké's year of birth is disputed. Many sources claim it is 1954, while others claim it is 1946. He was born in Yellou, a town near Niger's capital, Niamey. He entered the Niger military, rising to the rank of Major. On April 9, 1999, he led a military coup in which President Ibrahim Baré Maïnassara, who himself had come to power in a military coup, was assassinated. For two days there was much political uncertainty in Niger, as the Prime Minister, Ibrahim Hassane Mayaki and several others also had claims on the Presidency. On April 11, 1999, Wanké became President, heading a transitional government which promised to hold elections later that year.
Wanké's government fulfilled its promise, and turned over power to the newly elected president, Tandja Mamadou in December 1999. Wanké had many health problems, including cardiovascular troubles and high blood pressure. During the last months of his life, he traveled to Libya, Morocco and Switzerland for medical treatment. He finally died in Niamey. He is survived by a wife and three children.