If you file a European Patent you will get a provisional protection after publication, as it is described in Art. 67 EPC. If a state requires so, your provisional protection may start from the publication in a local language, e.g. after translation in the given language is provided. Art. 67 EPC is referring to Art 64 EPC which describes the inventors rights after grant.
Art. 67(1) EPC:
A European patent application shall, from the date of its publication, provisionally confer upon the applicant the protection provided for by Article 64, in the Contracting States designated in the application.
Art. 67(2) EPC:
Any Contracting State may prescribe that a European patent application shall not confer such protection as is conferred by Article 64. However, the protection attached to the publication of the European patent application may not be less than that which the laws of the State concerned attach to the compulsory publication of unexamined national patent applications. In any event, each State shall ensure at least that, from the date of publication of a European patent application, the applicant can claim compensation reasonable in the circumstances from any person who has used the invention in that State in circumstances where that person would be liable under national law for infringement of a national patent.
That is, in countries where no translation into a local langue is required, you may sue the infringer based on your provisional protection 18 months after filing the application. If however your application does not get granted, they can and most probably will sue you back.