Hadronic matter is soft.

The stiffness of the hadronic equation of state has been extracted from the production rate of K+ mesons in heavy-ion collisions around 1 AGeV incident energy. The data are best described with a compression modulus K around 200 MeV, a value which is usually called "soft." This is concluded from a detailed comparison of the results of transport theories with the experimental data using two different procedures: (i) the energy dependence of the ratio of K+ from Au+Au and C+C collisions and (ii) the centrality dependence of the K+ multiplicities. It is demonstrated that input quantities of these transport theories which are not precisely known, such as the kaon-nucleon potential, the deltaN --> NK+lambda cross section, or the lifetime of the delta in matter, do not modify this conclusion.