On 15 August , Japan issued Germany an ultimatum demanding the handover of the Kiautschou Bay concession .
That German ships abandon Chinese waters , thus intervening into World War I on the side of the Triple Entente .
On 15 August , Japan issued Germany an ultimatum demanding the handover of the Kiautschou Bay concession and that German ships abandon Chinese waters , thus intervening into World War I on the side of the Triple Entente .