Examples of attritional warfare by smaller countries:

1. WWI Italy vs the Austro-Hungarian empire. In Friuli I hiked the trails where the fortifications and trenches where they fought from 1915-1917 at 1500-2000m elevation, hauling artillery to mountain summits.

2. Serbia vs the Austro-Hungarian empire in WWI.

3. France vs Germany in WWI and Austria-Hungary vs Russia in WWI.

4. Finland vs the USSR in the Winter War.

5. the Confederacy vs the Union in The Wilderness and in Petersburg in 1864-65.

6. If you count insurgency wars as attritional: Vietnam vs France and the US. Dienbienphu was definitely attritional. Watch the hyperrealistic French movie Dienbienphu on YouTube if you have any doubts.

7. Israel vs Egypt and Syria, 1967-70.

8. Iraq vs Iran, 1980-88.

9. The Balkan Wars, 1912-13.

I could list many more.