That's just simply not true.

Like in the Crimea the Russian military entered just without official insignia so they could not be spotted officially.
Many pro-Russian fighters cross the boarder into Russia to be trained and equipped by the Russian military.
Proxy/Puppet states have already been established the Ukraine/Russia border in the region is de-facto non existent
http://en.wikipedia.org/wiki/Novorossiya_(confederation)
http://en.wikipedia.org/wiki/Donetsk_People%27s_Republic
It simply is true though David. Where is the picture from so we can actually discuss the authenticity of it? If it is from Crimea then Russian troops have always been there because there are military bases there. The truth is that our governments have offered no evidence of Russian troops entering Ukraine and you posting an unattributed picture isn't evidence either.
Where and when is this picture allegedly from? If you believe that Russia has invaded Ukraine then I've got a bridge you might be interested in. It seems odd that the evidence which eludes our own intelligence services is nonetheless available to you.
I suspect that there will be as much mileage in this invasion claim of yours that there was in your rather dismal list of alleged Russian aggression earlier in the thread. You didn't respond to the reply that I gave so am I now to assume that you accept that Russia has not launched any wars of aggression in the last thirty years or so? and that the US/UK have?
Remember also that being involved in Afghanistan at the request of the Afghan government of the time is not viewed the same as invading a country in an aggressive war.
If you don't know the difference read up on Nuremberg. International law and precedent regards a war of aggression as the ultimate war crime.
The fact that some Russians cross the border to fight in the civil war is hardly surprising and nor is it evidence of a Russian invasion. The east of Ukraine is largely ethnic Russian and there are many Russians with family in the east who are under bombardment from government forces. A civil war is raging in Ukraine between the east and west and it is clear that the eastern provinces will not accept rule from the current government in Kiev.
Crimea voted overwhelmingly to join Russia and if you understood any of the history and ethnic make up of Crimea then you would not be at all surprised by this. The coup in Kiev brought to power the sort of people that the east of the country would never accept and the country inevitably descended into turmoil.
I could give you lots of examples of UK citizens fighting in civil wars throughout history but no-one would claim that this is evidence of a UK invasion. When UK citizens fought in the International Brigades during the Spanish Civil War would that constitute an invasion by the UK? Are British jihadists in Syria evidence of a UK invasion of Syria? I could go on but I am sure you can fill the gaps in yourself.
There simply is no Russian invasion of Ukraine. The Minsk agreement acknowledges this implicitly. You are swallowing hook line and sinker the propaganda being fed to you by the same media that have been shown to be dishonest and lacking even a modicum of intellectual curiosity time and time again.
The same media that tried and convicted Christopher Jeffries and many others using innuendo and gossip are now employing the same method to convict Putin of pretty much everything bad happening around the world. Evidence is what matters not gossip. Rather than an unattributed picture can you post any evidence of the Russian invasion. Do you honestly think that the Ukrainian Army would not have been overrun within days if the Russians actually did invade? If you honestly believe that the Ukrainian Army could engage an invading Russian Army in a war of attrition rather than being brushed aside in days then you are mistaken.
The usual suspects are pushing for war yet again but this time against a nuclear superpower so there really are WMD.
We have our own problems at home with our megalomaniac politicians and unsolved murders and should probably care more about putting our own house in order rather than concerning ourselves with Putin and Russia.
Nemtsov is a fine example of this. Nemtsov had between 1 and 5% support in Russia and was barely even a fringe figure. His party has no MP's in the Duma and has not had any for 13 years. He was Yeltsin's DPM and was largely reviled in Russia for being party to the looting of Russia's natural resources during the chaotic reign of Yeltsin when a few criminals became billionaires. He has been described as "Opposition Leader" when nothing could be further from the truth. The Communist Party is by far the largest opposition in Russia to Putin's United Russia. Calling Nemtsov "Opposition Leader" is akin to calling Nick Griffin "Opposition Leader". If Nick Griffin were shot outside the House of Commons and the Russian press started blaming Cameron and talking of Griffin as a political rival you would think them bonkers and you would be right. But we are expected to believe that Putin had a political nobody murdered in full view outside the Kremlin.