I believe the answer is:
They showed the strength of Christian belief.
Martyr refers to the people who are willing to sacrifice their life for a certain cause. In the past, many Christian missionaries become a martyr by defending their religion in the face of torture and execution.
As the news of their death spread, they indirectly showed the strength of their belief which ignite other people's will to adopt the religion.
We show that municipalities that are exogenously exposed to the Drug War experience a 40% decrease in export growth on the intensive margin. Large exporters suffer larger effects, along with exports of more complex, capital intensive, and skill intensive products. Finally, using firm level data, we provide evidence consistent with violence increasing marginal exporting costs.
The conflict between the southern and northern states did not start suddenly with the attack on fort Sumter , it long predates the 1860's.