Results are mixed:

[link to online.wsj.com]

But the real problem is that any time Ukrainian forces advance, the rebels get more lethal assistance from Russia (despite Putin's deceitful denials):

[link to www.washingtonpost.com]
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But when the artillery fire comes from Russia, they cannot respond.

Most of the fire is directed from Russian territory.
...
Grad rockets fired from Russia and by separatists inside Ukraine land almost every day and night.
...
“Two days ago, we took out four Russian trucks, one tank and an armored personnel carrier crossing the border,” he [a Ukrainian captain] says on a phone line that crackles with static.

“We’re not under fire now, but in the night we were shot at by artillery and Grads. It lasted for 3 1 / 2 hours. It came from Russia. It’s not coming from the Donetsk People’s Republic or the Luhansk People’s Republic. Sometimes the DPR and the LPR fire at the Russians, trying to provoke them to fire back. . . . But we’re under strict orders not to fire into Russia. If we shell them, they will attack us.”
...
“The situation is difficult because they can’t fire back at the Russian side,” he said.
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Clearly the only long-term solution to this is to bring Ukraine into NATO. Ukraine, like Poland and Lithuania, will never be truly free until it has guaranteed protection against its rapacious neighbor to the east.