Singapore’s President Halimah Yacob and Prime Minister Lee Hsien Loong have written to Indonesian President Joko Widodo to express their condolences over the death of 53 crew members on board a sunken submarine. Faculty at RSIS have also extended their condolences over the death of Lieutenant Colonel Heri Oktavian, their alumnus and the ship’s commander. Lt Col Oktavian was postgraduate student at RSIS in 2014 and did a Master of Science in Strategic Studies, said the school on Monday. He had been commander of the KRI Nanggala 402 since April last year, according to Indonesian media.