How many tanks (including tankettes) did Poland have at the beggining of WWII?

Soviets. An­ti-­tank dogs were taught to carry ex­plo­sives to tanks. The original idea was for a dog to release the bomb and return to the op­er­a­tor, but it was un­suc­cess­ful and replaced by an impact det­o­na­tion pro­ce­dure. The U.S. military trained an­ti-­tank dogs in 1943 for use against for­ti­fi­ca­tion­s, but never deployed them.

Battle of Cambrai. Modern scholars do not place ex­clu­sive credit for the first day on tanks but discuss the con­cur­rent evo­lu­tion of ar­tillery, infantry and tank methods.

To estimate total tanks pro­duc­tion. The allies found out, that the gearbox numbers fell in two unbroken se­quences, so large pro­duc­tion resulted in influx of large serial numbers. Today, the problem of es­ti­mat­ing the maximum of a discrete uniform dis­tri­bu­tion from sampling without re­place­men­t, is known - in the En­glish-s­peak­ing world - as the German tank problem.

Type 97 ShinHoTo Chi-Ha. The Type 97 ShinhoTo Chi-Ha was a Japanese medium tank used in World War II that was an upgrade to the original Type 97 Chi-Ha. The new version was des­ig­nat­ed Type 97-Kai ("im­proved") or Shinhoto Chi-Ha ("new turret" Chi-Ha). This design was probably the best tank Japan produced in any large quantity up to 1945.