MOSCOW, July 30 -- Eight months before they gather in Red Square's shadow, the leaders confirming their attendance in Moscow keep coming. South Sudan's Salva Kiir is the latest, his written commitment to Vladimir Putin delivered through diplomatic channels on Tuesday, making him the seventh African head of state known to have formalized participation in the third Russia-Africa Summit, set for October 28 and 29.

The announcement came from the Russian Embassy in Juba after the South Sudanese foreign minister hand-delivered Kiir's letter to the Russian side. Moscow did not hold a ceremony around it. It did not need to. The accumulation of names on the guest list is the statement.

That list now includes Burundian President Evariste Ndayishi...