Closely trusted but rarely heard, he seems to have been an intensely private figure, in some ways not even that well-known to the presidents who entrusted themselves to his protection.
It was known that his relations with Mr Bazoum, a longstanding ally of Mr Issoufou, were more distant and in recent weeks there were rumours that the president was preparing to force him into retirement.
Perhaps personal resentments had accumulated, unexpressed but still powerful.
Removal from his post, even at a fairly normal age for retirement, would certainly have come as a painful blow for a man who over four decades has gradually climbed the promotion ladder, after starting out as an ordinary soldier.
Gen Tchiani is from the majority Hausa ethnic group, and comes from Tillabéri region, a traditional recruiting ground for the military.
Yet he is not from the typical officer corps background or with obvious political connections. He has had to work his way up from the base.
Mr Bazoum is also someone who came from a fairly modest background and then gradually climbed the educational and career ladder, in his case at university and then as a secondary school teacher and trade unionist, before going into politics in the early 1990s.
But curiously, Gen Tchiani never really established a comfortable working relationship with Mr Bazoum – whereas he seems to have got along more easily with Mr Issoufou.
Now of course, after so many years out of the public eye, Gen Tchiani finds himself on a crash course in political and diplomatic crisis management.
So far he has relied on what has served him best over the long years in the military: restraint, a cautious reluctance to fully speak his mind before others, and a refusal to compromise.
But Gen Tchiani and the junta have cleverly touched a chord of anti-French resentment among many Nigériens and they will try to turn this into a wider base of support and defiant popular backing for the confrontation with Ecowas.
And as this testing face-off against Nigeria and other members of the West African bloc plays out over the coming days, and sanctions bite ever harder, driving up the cost of living for ordinary people, these newfound populist and political skills will be ever more critical as the general plays the highest-stakes gamble of a previously careful career.
Paul Melly is a consulting fellow with the Africa Programme at Chatham House in London.