We will discuss the missing pieces in the understanding of the effective field theory description of string creation, the S-dual of the Hanany-Witten effect, both in the open and closed string picture. We explain the origin of a crucial bare Chern-Simons term, that used to be added in by hand for consistency. Finally we summarize the remaining unsettled issues, concerning the need to modify the DBI action and the interpretation of the bare term in M-theory.