Laika herself was a Soviet Dog that belonged to the Soviet Union meaning that the Soviet Union itself was the first country to send the first dog into space and was launched on November 3 1957.
Because in 1957 since before the first man (Yuri Gagarin) was launched into space which was first attempted on April 12 1961 we didn’t actually know from whether or not a human being could be able to survive in space and in order for them to prove and know that a human could be able to survive in space they then subsequently launched a dog out into space instead of a human.