Complex sentence: The sole condition attached to the release of Chief Abiola was that he renounce his mandate, something that he refused to do, although the military government offered to compensate him and refund his extensive election expenses.
Split into simpler sentences: The sole condition attached to the release of Chief Abiola was that he renounced his mandate. Something that he refused to do, even though the military governemnt was offering to compensate him and refund his extensive election expenses.