What is a short poem written in pairs of unrhymed lines often on themes war love or death?

Here's a breakdown:

* Tanka is a Japanese poetic form.

* It consists of five lines with a specific syllable count:

* Line 1: 5 syllables

* Line 2: 7 syllables

* Line 3: 5 syllables

* Line 4: 7 syllables

* Line 5: 7 syllables

* It often explores themes of nature, love, and the human condition (including war and death).

* Rhyme is not required.

Let me know if you'd like to see an example!