Maybe it's just me but I don't read four weeks as shortly given the situation. And why does he feel a need to announce it?
The Germans have a lot of restrictions to prevent politicians from just doing stuff, without first telling the public.
That goes double for stuff that involves German military equipment outside Germany, and triple for the deployment of German tanks in Eastern Europe.
Can you think of any reasons why that might be?
"Once all the Germans were warlike, and mean,
But that couldn't happen again.
We taught them a lesson, in nineteen eighteen,
And they've hardly bothered us since then..."
- Tom Lehrer,
MLF Lullaby
We should also remember that both WWI and WWII were essentially wars between Germany and Russia, wherein they fought over possession of the territory that used to be the Polish-Lithuanian Commonwealth--Poland, Belarus, and Ukraine. Between the wars, Poland had been restored, and WWII started as a Hitler-Stalin collaboration designed to split it into two pieces, each side reclaiming territory it perceived as having been lost at the end of WWI. Stalin won WWII and gobbled up half of Poland, ethnically cleansing it of Poles and shifting Polish territory into a large chunk of former German territory. Now we have Poland strongly supporting Ukraine against their traditional enemy--an expansionist Russia--and Germany is being asked to get involved in that conflict again. The historical context in that region might make the Germans a bit more reluctant to be seen as a major arms supplier to Ukraine, which it had brutally occupied for most of the WWII period.
Seems to me if Germany was largely responsible for the offensive destruction of Ukraine during WWII, they might feel some sense of obligation to defend the same.
Frankly, I don't think Germany today has any policy regarding Ukraine. Unless prevarication is a policy.
Actually, the Nazi occupation of Ukraine was as brutal, if not worse, than the Russian occupation. Stalin had starved roughly 3 million Ukrainians to death in the Holodomor, when he imposed collectivization on the agricultural economy. Most of the food was stolen by the Russia-dominated Soviet regime and sold to foreigners for hard currency. Germany was a big customer and continued to benefit from Ukrainian bountiful harvests until they invaded and occupied Ukraine. Since Stalin had killed or deported most of the ethnic Polish population from Belarus and Ukraine during the Great Terror in 1937-1938, Ukrainian nationalists had hoped for an invasion from Poland to drive the Russians out. However, Poland signed a non-aggression pact with Stalin, destroying that hope. Then they looked to Germany for some intervention to relieve them, but the Nazis proved to be even worse than the Soviets. Hitler saw Ukrainians as subhumans to be eliminated or deported to make way for more superior German farmers. Hence, he kept Stalin's system of collectivized agriculture in place, leading, again, to widespread starvation. And he killed off much of the huge Jewish population in Ukraine, often with the help of non-Jewish Ukrainian nationals. Reprisals against Ukrainians were common whenever partisan activity hindered German operations, and Ukrainians were often used as human shields.
So, if you think Germany was not largely responsible for the offensive destruction of Ukraine during WWII, I think that you are wrong. They were primarily responsible for it, because much of the most destructive fighting took place in Ukraine, Belarus, and Poland. Much of the Soviet Red Army that conquered Germany was made of Ukrainians and Belarusians, who were glad to see the German occupiers pushed out, even if it meant a return of the Russians. When Germans captured Soviet soldiers, a great many of whom were Ukrainian, they packed them into concentration camps and systematically starved them to death. I don't think that Germans feel an obligation to defend Ukraine. I think that they would rather forget what they did in Ukraine and what Soviet Ukrainians did to them in retaliation.
(My source for much of the above is Timothy Snyder's recently-published history called
Bloodlands).