Zimbabwe's ruling party, Zanu-PF, and the military may be fracturing along generational lines but many underestimate party members and officers' determination to stay in power as the 2018 general elections approach, former Education Minister David Coltart has claimed.

After decades of quelled frustrations under President Robert Mugabe's iron-fisted rule, the country has been rocked by grassroots protest movements calling for change as the ruling party splits over who will succeed him (read below: Is Zimbabwe's military splitting?).

The reportedly divided Zanu-PF will seek to extend its 36-year rule in the 2018 general election, but opposition political parties, which are hoping to force Zanu PF out, remain deeply disorganised despite a number of coalitions already in place.

Speaking to IBTimes UK, Coltart, who was Minister between 2009 and 2013 under the opposition MDC and Zanu-PF coalition government, claimed Zanu-PF officials will "do anything in their power to hang on" come 2018.

"It's hard to envision real change in 2018, partly because of the reality on the ground," the politician said from the nation's second-largest city, Bulawayo.

Africa's oldest head of state faces a real threat of split within the armed forces, which could endanger the cohesion of his power base within Zanu-PF, but General Constantine Chiwenga, the commander of Zimbabwe Defence forces (ZDF), last month vowed his forces will stand by the embattled president.

Zimbabwe's military has had a critical role in politics since the independence war against the white-minority state of Rhodesia.

'We have underestimated the determination of the military to hold on to power'

"In the past we have always underestimated the determination of the military in particular to hold on to power. The division between the military hierarchy and Zanu-PF hierarchy has always been very difficult to differentiate," Coltart explained.

"There has been so much fusion between the two. Even if Mugabe retires or dies, I still think that you're going to have this streak of former war veterans - and now we also see this in people within the military - they will do anything in their power to hang on."

Coltart, a veteran human rights lawyer, said he believes that only a complete fusion of Zimbabwe's different parties under one political party will bring change in the 2018 general elections.

"A grand coalition is certainly something that we need. The division in the main opposition has been a gift to Mugabe and Zanu-PF. But there is a growing realisation that we can't afford the luxury to remain divided - all these opposition parties are divided on personality rather than policy.

He added: "I am hopeful that there will be more cohesion but we have a long way to go yet. The ideal, of course, is to see not just a coalition but a complete fusion of these different parties under one political party - that would be the ideal. While I think that's probably a bridge too far, what would be hopeful is at least a coalition in which you don't split the votes but agree on a single opposition candidate for president."