South Sudan President Salva Kiir replaced his vice president and rival Riek Machar yesterday, a move that could potentially undermine last year's peace deal and reignite war in Africa's youngest nation. Machar was sworn in as first vice president only last April, eight months after a peace agreement that ended two years of fighting that broke out the last time that Kiir sacked him as his deputy in 2013. But the rivalry between the two men led to deadly violence in the capital Juba early this month and Machar has not been seen since the clashes. James Shimanyula reports..