In 2013, I was working with the United Nations peacekeeping mission in South Sudan (UNMISS) as the head of the small arms and light weapons unit.

One afternoon I was invited by senior members of the army to visit their weapons store near the main army barracks in Juba.

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The store contained weapons procured from Germany, Belgium, Hungary, the Soviet Union, Ethiopia, China, and Israel.

Many of the weapons were decades old.

A few weeks after my visit, in December 2013, senior officers, under orders from the highest levels of government, took these weapons from the stores and passed them to militias that proceeded to kill thousands in ethnically-motivated massacres.

I subsequently left UNMISS to join the UN Security Council Panel of Experts to investigate and trace the use of these arms during the five-year civil war that followed the massacres in Juba.

Many of the weapons used in the atrocities had not been sold directly to South Sudan but rather to its neighbours, particularly Uganda.

When we approached the countries that had supplied the weapons, their response was uniform: the weapons had been sold in good faith with the aim of improving security, and their use in ethnic violence was not intended or foreseen.

In other words, selling weapons to Uganda was done to support a reliable partner and fostering influence to work collaboratively on regional issues, such as counter-terrorism operations in Somalia.

Uganda, however, saw the weapons also as an opportunity to pursue its own strategies in various regional conflicts and did not acknowledge that these weapons had been used in atrocities in South Sudan.

I thought of these experiences when I recently learned that the European Union is developing a European Peace Facility (EPF) that includes a component to train and equip foreign government military actors in fragile states by, among other things, providing weapons.

This would be new terrain for the EU because its existing instruments prohibit the direct provision of lethal technology to foreign government partners.

The expressed aim of the EPF would be to expand the EU's options for supporting fragile states and thereby deepen defence cooperation and influence in the security sector of these target countries.

Crucially, the European Parliament would not, for now, have any formal oversight over decisions made under the EPF.

This week, European parliamentarians are expected to adopt their own position on the EPF in Strasbourg and may recommend having more oversight.

Instead, scrutiny of the impact and efficacy of EPF decisions would be left to national parliaments. This would create further separation between the donors and the recipients of weapons, likely diluting not enhancing accountability.

South Sudan illustrates several important considerations for the EU as it embarks down this path.

Small weapons, long life-span

Firstly, weapons, particularly small arms, potentially have a very long service life span.

They can, and often are, used years later and in very different contexts from those originally envisaged.

This creates a fundamental difficulty in assessing and managing risk when providing lethal technology, particularly in environments that are fragile and inherently unpredictable.

Secondly, providing weapons to government security services in fragile countries does not reliably lead to greater influence and an ability to determine how and when the weapons are used.

Uganda has long been a military partner of Western countries and a major recipient of defence cooperation and support.

However, Uganda has also consistently diverted weapons into conflicts in direct opposition to Western efforts to restrain the violence in South Sudan.

The influence and partnership that Western donors have sought with Uganda through the provision of weapons and other military equipment have remained unreliable and often illusory.

The idea that the EU can develop effective influence through providing weapons is further undermined when you consider that Russia, China, Iran, and others also use weapons in this way.

There is a distinct risk that rather than creating influence, the EU will be pulled into competition with rivals who will constantly seek to undercut EU programs through the provision of more attractive weapons deals.

South Sudan has been masterful in playing off various donors in seeking deals with few effective restrictions.

Lastly, there is a high likelihood that, even with mitigation strategies in place, some weapons provided to fragile countries will be used to commit atrocities.

Israel was highly embarrassed when new weapons provided to South Sudan's National Security Service in November 2013 were, a month later, used to massacre civilians.

When atrocities occur, there is a common instinctive response to avoid accountability.

If EU-funded weapons were used contrary to the purpose intended the prospect of this leading to attempts to cover up or otherwise evade accountability are high.

Whatever the motivations of the EPF, the risks of this fund resulting in significant damage to the EU's reputation and principles are high.

It would be prudent for EU member states to carefully consider if it is wise to proceed down this path as they debate the EPF over the coming months.