Russian troops have spent the past several months constructing intricate fortifications in Ukraine. Ukrainian troops now have the tough task of fighting their way through those trenches and barriers. Current Russian fortification doctrine has seen "little methodological change" since the Cold War, according to the RUSI report. BEN STANSALL/AFP via Getty ImagesClearing minefields is difficult because Russian mines have multiple triggers and anti-tampering devices. In addition, Russia did not sign the 1997 Ottawa Treaty banning anti-personnel mines, which has allowed its forces to "freely utilize victim-initiated" anti-personnel mines, RUSI said.

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