Joschka Fischer, leader of the Greens, had hoped to avoid confronting this issue - and his party's pacifist wing - until he is safely installed as Foreign Minister. But under pressure from Washington, Germany's incoming and outgoing leaders agreed to convene the Bundestag for Friday, two weeks earlier than originally planned.
If Mr Fischer, who supports intervention, is abandoned by the majority of the Greens, his claim to the foreign ministry will be all but scuppered.
In recent years, the Greens have softened their all-out opposition to soldiering, but many members continue to view violence as a last resort, to be used only in extreme circumstances.
Party policy dictates that decisions about an intervention should not be left to Nato, an organisation which the Greens' national conference wanted abolished earlier this year.
"A UN mandate is needed for such a mission," commented Ludger Volmer, the leading "Fundi" in parliament. Since no UN mandate is forthcoming, Mr Volmer might vote against the decision to send 14 Tornado aircraft and 500 German soldiers to the Balkans. Yesterday he refused to say which way he will cast his ballot.
In the past, the Greens split over troop deployment to Bosnia, for instance. At that time though, they were in opposition. Mr Fischer's claim to the foreign ministry rests on the assurance that he has since tamed his pacifists.
The crisis in Kosovo has come at a very inopportune moment for all German politicians.
Helmut Kohl and his ministers have clearly lost their zest for governing since their election defeat last month. Yesterday they finally issued the "activation order", which must, however, be approved by parliament. But a new parliament has yet to be convened, because Gerhard Schroder's Social Democrats and Mr Fischer's Greens are involved in protracted coalition talks.
Embarrassingly, MPs from the old Bundestag, many of whom lost their seats, must gather on Friday to provide the necessary stamp of approval. A majority is not in question, but whether the Greens have matured to reliable coalition partners now is.
Not that the Social Democrats are setting a good example. While the US and the other allies await some action in Bonn, Mr Schroder's colleagues are busily hatching Byzantine plots against one another.
Yesterday they finally resolved the power struggle over the defence ministry and the position of the chief party whip, but in all the confusion ended up with one Social Democrat too many in the new cabinet. The understudy for Foreign Minister Fischer, perhaps?