The UK's Ministry of Defence (MoD) says the first batches of Russian men drafted in to fight in Ukraine have started arriving at military bases.
But it says training them could be tough, as many have limited military experience, or it's out of date.
Last week Vladimir Putin announced 300,000 more troops will be drafted in to fight in the conflict with Ukraine.
For Tim Cross, ex-president of the Armed Forces Christian Union and a retired Major General, Putin's move poses a major risk.
"These mobilizations are not going to happen quickly," Cross told Premier Christian News.
"It will take some time before those numbers begin to arrive in any significant shape in the next few weeks, so how quickly they can reinforce that front?
"The danger is Putin and his generals will see them as simply cannon fodder, to put in huge numbers, in an attempt to just roll over the Ukrainians and retake this territory that they've lost over the last month or so.
"There's a real danger here that these guys will not be trained properly, they'll not be equipped properly, and that they will find themselves in in difficult situations to put it politely."
On Monday, a conscription office was set on fire in protest of the call-up of the thousands of additional soldiers to fight in the conflict with Ukraine.
Cross said prayer is needed not only for the Ukrainians fleeing the war but for the Russian soldiers too.
"We need to be very careful about just saying all Russians are bad, all Ukrainians are good.
"We know that as Christians, we're all flawed people and we're all part of the problem.
"So we need to pray for those young Russian soldiers who are being mobilised, we need to pray for the people in Russia who are trying to get their mind around what's going on.
"We need to pray for people like Putin and Patriarch Krill, the Russian Orthodox Church, who are supporting this campaign."