I went skiing in Korea during the next to last weekend of Feb 2020. Best skiing of my time there, because the mountain was already empty of people due to public concern. By that time we were already wearing N95 masks: I remember discovering it was very hard to talk with both a ski mask and an N95 on.

By mid Feb, Korea was already covertly acquiring mask materials and preparing a ramp up in testing. I believe we had working PCR tests in my local hospital by mid March, and mask rationing in April. This made me very skeptical of the competence of the US public health establishment.

Edit: Skiing was Feb 21 to 23, just before Daegu locked down. The Mask rationing started early March: https://m.koreatimes.co.kr/pages/article.asp?newsIdx=292662