refrained from a critical reaction

France and Britain refrained from a critical reaction to the Soviet invasion and annexation of Eastern Poland since neither country expected or wanted a confrontation with the Soviet Union at that time. Under the terms of the Polish-British Common Defence Pact of 25 August 1939, Britain had promised assistance if a European power attacked Poland. A secret protocol of the pact, however, specified that the European power referred to Germany. - это Wiki

просто Wikipedia nothing more

а secret protocol no shit