To begin with, neither side had pilots qualified for the planes and relied on pilots and technical staff from the former Soviet Union to fly and maintain them.
Both sides have been stockpiling weapons for at least two years.
And tight budgets have not excluded high-tech elements from the shopping lists.
In the 10-month lull in fighting between 1999 and 2000, Ethiopia also purchased a number of Sukhoi 25, a heavily-armed low-level ground attack aircraft well suited to punching through trench formations that have dominated the fighting.
Million dollars a day
Both sides are estimated to have been spending about $1m a day since the conflict broke out in May 1998.
The new Russian aircraft represent a significant step up from the MiG-21 and MiG-23 fighters left over in the Horn from the previous military dictatorship of Mengistu Haile Mariam.
To begin with, neither side had pilots qualified for the planes and relied on pilots and technical staff from the former Soviet Union to fly and maintain them.
Local pilots have now been trained up, but the sophisticated fighters have not been greatly in evidence in the fighting.
There have certainly been some losses, with two of the Eritrean MiG-29s confirmed shot down in 1999, while there are Eritrean claims that a Sukhoi 27 was downed in the latest upsurge in fighting.
Gunships
Both sides have also bought helicopters. Eritrea obtained attack helicopters from Italy, to add to the four given to it by Ethiopia in 1995 at the time of its conflict with Yemen over the Hanish Islands, and never returned.
Ethiopia also bought helicopter gunships and attack helicopters from Russia in December 1999 to add to its existing fleet.
Both sides have also been building up their armouries, buying arms and ammunition widely.
Eritrea got material, including rocket supplies for its BM21 multi-barrelled rocket-launchers, known as "Stalin's Organs", from Bulgaria, flown into Asmara by Ukrainian planes.
Ethiopia has been supplied with Chinese ammunition and more than 100 T-55 tanks from Bulgaria.
Addis Ababa was in negotiation with an Israeli company to upgrade and refurbish 50 mothballed MiG-21 and MiG-23 fighters.
Agreement was reached but then delayed because of Eritrean complaints - Israel wanted to remain friendly to both countries and the deal was postponed.
Foreign donors
In the meantime, Ethiopia acquired its Sukhoi fighters, and a team of at least 100 Russian technicians, part of whose job is get some of the older MiGs back into the air. France has also supplied communications equipment.
Funding has been difficult for both sides as most of the new equipment has had to be paid for cash in advance, though there were reports that Ethiopia may have bartered coffee with China.
Eritrea has obtained funds from the Gulf, particularly Qatar, and Libya.
This latter source has caused considerable concern in Washington and Tel Aviv and observers say Israel may well have reactivated its interest in Ethiopia's MiGs in response.
Asmara has also raised funds from treasury bonds and from the diaspora population.
Ethiopia has increased its military budget, and it, too, is raising money from Ethiopians abroad, and using "voluntary" donations locally to provide for food and medical supplies for the troops.
Conscripts and volunteers
Both sides have increased the size of their armies from a pre-conflict level of 50-80,000 to their present 300,000.
For Eritrea, that means conscription and the mobilisation of a staggering 10% of the population.
Ethiopia - with a population of 60 million - maintains a regular army, but its recent massive expansion has brought in new troops with no more experience than the Eritrean conscripts have.
Tens of thousands of soldiers on both sides have been killed in the fighting.