Breakdown of Pass auf, der Feind ist am Angreifen!
sein
to be
aufpassen
to pay attention
am
on the / at the
der
who, which, that (relative pronoun; die, das)
Questions & Answers about Pass auf, der Feind ist am Angreifen!
How does the colloquial am-progressive work in this sentence?
To show that an action is currently ongoing, colloquial German often uses a form of sein (here, ist) plus am followed by the verb's infinitive. Because am is a contraction of the preposition an and the article dem, the verb turns into a neuter noun. That is why Angreifen must be capitalized here.
Could I just say der Feind greift an instead?
Yes, absolutely! Standard German usually relies on the simple present tense (greift an) for both "attacks" and "is attacking". The am-progressive is mostly used in spoken German when you really want to emphasize that the action is in progress right at this exact moment.
The verb angreifen is separable. Why isn't it split up into am greifen an?
Because it is functioning as a noun in this grammar structure. When you nominalize a separable verb to use it with am or beim, the prefix and the verb stay glued together as one single capitalized word: das Angreifen.
Just as a refresher, why is the first part of the sentence Pass auf rather than Passt auf?