Iraq's campaign to take back the western section of its second-largest city, Mosul, from so-called Islamic State (IS) will be Baghdad's last major showdown with the group, which, at its height, had controlled a third of the country's territory, reports BBC.
This will also be the toughest fight yet, as losing its most cherished prize will present IS with an existential challenge incomparable to any other loss it has suffered over the past two years.
Four months ago, Iraqi Prime Minister Haider al-Abadi announced the official start of comprehensive operations to retake all of Mosul - east and west.
The timing of the announcement of the latest phase of the campaign has more to do with rallying the morale of his beleaguered forces than any significant changes in military
strategy.
The fight for the east proved more difficult and time consuming than the Iraqi government had predicted.
The initial hope from the Barack Obama administration had been that Mosul would be liberated before the handover of power in Washington.
It is become clear that liberating all of Mosul will take several more months.
In taking the east of Mosul, the Iraqi Security Forces (ISF) suffered considerable losses. According to Pentagon insiders, the casualty rates for certain forces on the front line was as high as 50%. While this figure is denied by Iraqi military personnel in Baghdad, the government is concerned with attrition rates.
In battle, a winning side could be expected to suffer a much lower casualty rate. Incurring considerably more losses would heighten the risk of combat ineffectiveness.
For Prime Minister Abadi, just as important as weapons and funding is ensuring that his fighters on the frontline maintain battlefield morale and so far they have done so.
Time, however, is not on his side, as a prolonged campaign could erode troop resolve.
Mosul is the IS heartland. It was here, in the west, that the group's leader, Abu Bakr al-Baghdadi, made his first and only public appearance, at al-Nuri mosque.
What has become clear from the battle thus far is that IS fighters will not retreat as easily from Mosul as they did in Falluja and Ramadi.